feat(grpc): PSK-authenticate the site gRPC control plane; drop the vestigial management receptionist registration

Phase 0 of the ClusterClient→gRPC migration
(docs/plans/2026-07-22-clusterclient-to-grpc-plan.md). Standalone hardening: it
closes a gap that exists today and is a precondition for moving command/control
onto gRPC in later phases.

T0.1 — delete the ManagementActor ClusterClientReceptionist registration.
It was built for an out-of-cluster CLI that was never written: the shipped CLI
speaks HTTP Basic to /management, which asks the actor in-process through
ManagementActorHolder. Nothing in the repo ever sent to /user/management. The
actor still runs there; only the cross-boundary advertisement is gone. Six
documents claimed the CLI used ClusterClient — including the CLI's own README
"Architecture Notes" — and are corrected here rather than left to rot.

T0.2 — record, do not port, the dead integration-routing path.
IntegrationCallRequest is unwired at BOTH ends: RouteIntegrationCallAsync has
zero callers anywhere, and RegisterLocalHandler(Integration, …) appears only in
a test, so production always answers "Integration handler not available". It is
excluded from the gRPC contract (28 of 29 commands migrate) rather than
enshrined on an additive-only wire format, and deleting it during a
transport migration would mix a behavioural change into a change whose whole
value is that behaviour is identical. See
docs/known-issues/2026-07-22-integration-call-routing-is-dead-code.md.

T0.3 — preshared-key authentication on SiteStreamService.
The service shipped with no auth at all: plaintext h2c, no interceptor, so
anything that could reach a site node's :8083 could open a live data stream or
read audit rows back via PullAuditEvents/PullSiteCalls. ControlPlaneAuthInterceptor
now gates /sitestream.SiteStreamService/ — modeled on LocalDbSyncAuthInterceptor
(constant-time compare, fail-closed, PermissionDenied) but gating a SET of
service prefixes so phases 1A/1B add services rather than interceptors. LocalDb
sync keeps its own separate key: it authenticates the pair partner, not central,
and collapsing the two would make a site's central-facing key also admit writes
into its database.

Keys are per site (SB-GRPC-PSK-<siteId>), never fleet-wide, so a compromised
site yields only its own. Central attaches them through ControlPlaneCredentials,
which binds CallCredentials to the channel — covering unary and streaming
uniformly, and letting the key resolve asynchronously, which a client
interceptor could not do without blocking. All three central→site channel
creation sites go through it (SiteStreamGrpcClient and both audit pull invokers);
the pull invokers' channel caches are re-keyed by (site, endpoint) because
credentials are per-site and bound to the channel.

Two decisions beyond the plan:

  * StartupValidator now requires GrpcPsk on Site nodes. The plan specified only
    the runtime gate, but fail-closed with no boot check produces a node that
    joins, answers heartbeats and reports healthy while refusing every stream,
    audit pull and telemetry ingest — silent and total. Same reasoning as the
    existing inbound API-key pepper rule.

  * Added Communication:SitePsks as a central-side key map. The plan assumed
    central would read the store, seeded via a dev KEK; the docker rig
    deliberately boots with no master key, so store-only resolution would leave
    it unable to dial its own sites. The store stays primary — it is the only
    source that can serve a site added at runtime — with the map covering
    key-less hosts and one-off pins. Neither source falling back to
    "unauthenticated" is the invariant.

T0.4 — dev keys on both rigs and tests.
34 tests. The seven that matter most exercise a real in-process gRPC stack over
TestServer: the unit tests on either side of the wire would both stay green if
the halves disagreed, and gRPC refuses call credentials on a plaintext channel
by default — the UnsafeUseInsecureChannelCallCredentials opt-in is only provable
by making a real call. They confirm correct key passes on unary AND streaming,
wrong key and no-credentials both get PermissionDenied, and an unresolvable key
fails the call with nothing reaching the service.

OPERATIONAL: a site node upgraded to this build without a key will not boot.
That includes the gitignored deploy/wonder-app-vd03/ overlay.

docker/README.md

@@ -120,6 +120,31 @@ docker/
     └── logs/
 ```
 
+## gRPC control-plane keys (dev)
+
+The site gRPC service (`SiteStreamService` on 8083 — live subscriptions, audit pull,
+cached-telemetry ingest) is gated by a preshared key, and the gate is **fail-closed**: a site node
+with no key refuses every call, and `StartupValidator` refuses to boot it at all. So the rig
+carries dev keys, one per site:
+
+| Where | Setting | Value |
+|---|---|---|
+| `site-{a,b,c}-node-*/appsettings.Site.json` | `ScadaBridge:Communication:GrpcPsk` | `dev-grpc-psk-docker-site-{a,b,c}` |
+| `docker-compose.yml`, both central nodes | `ScadaBridge__Communication__SitePsks__site-{a,b,c}` | same value |
+
+Both nodes of a pair carry the same key; each site's key is different from the others'. The
+central half lives in compose env rather than the mounted `appsettings.Central.json`, which by
+convention holds no plaintext credentials. Production uses `${secret:SB-GRPC-PSK-<siteId>}` on
+the site and the matching secret in central's store — see
+[`docs/deployment/topology-guide.md`](../docs/deployment/topology-guide.md).
+
+**These are not real secrets and are committed deliberately**, exactly like the LocalDb sync key
+(`dev-site-a-localdb-sync-key`) beside them. The two are separate keys on purpose: the LocalDb one
+authenticates the *pair partner* for database replication, not central.
+
+If you add a site to the rig, add its key in both places or its streams will fail with
+`PermissionDenied`.
+
 ## Commands
 
 ### Initial Setup

docker/docker-compose.yml

@@ -27,6 +27,15 @@ services:
       ScadaBridge__Database__MachineDataDb: "Server=scadabridge-mssql,1433;Database=ScadaBridgeMachineData;User Id=scadabridge_app;Password=ScadaBridge_Dev1#;TrustServerCertificate=true"
       ScadaBridge__Security__Ldap__ServiceAccountPassword: "serviceaccount123"
       ScadaBridge__Security__JwtSigningKey: "scadabridge-dev-jwt-signing-key-must-be-at-least-32-characters-long"
+      # DEV-ONLY gRPC control-plane preshared keys, one per site — NOT real secrets.
+      # Central verifies/presents these; each site node carries the same value as
+      # ScadaBridge:Communication:GrpcPsk in its mounted appsettings.Site.json. Kept as
+      # env overrides (not in the mounted central appsettings) so that file stays free of
+      # plaintext credentials. Production instead seeds SB-GRPC-PSK-<siteId> into the
+      # secret store, which is also the only source that can serve a site added at runtime.
+      ScadaBridge__Communication__SitePsks__site-a: "dev-grpc-psk-docker-site-a"
+      ScadaBridge__Communication__SitePsks__site-b: "dev-grpc-psk-docker-site-b"
+      ScadaBridge__Communication__SitePsks__site-c: "dev-grpc-psk-docker-site-c"
     ports:
       - "9001:5000"   # Web UI + Inbound API
       - "9011:8081"   # Akka remoting (host access for CLI/debugging)
@@ -65,6 +74,15 @@ services:
       ScadaBridge__Database__MachineDataDb: "Server=scadabridge-mssql,1433;Database=ScadaBridgeMachineData;User Id=scadabridge_app;Password=ScadaBridge_Dev1#;TrustServerCertificate=true"
       ScadaBridge__Security__Ldap__ServiceAccountPassword: "serviceaccount123"
       ScadaBridge__Security__JwtSigningKey: "scadabridge-dev-jwt-signing-key-must-be-at-least-32-characters-long"
+      # DEV-ONLY gRPC control-plane preshared keys, one per site — NOT real secrets.
+      # Central verifies/presents these; each site node carries the same value as
+      # ScadaBridge:Communication:GrpcPsk in its mounted appsettings.Site.json. Kept as
+      # env overrides (not in the mounted central appsettings) so that file stays free of
+      # plaintext credentials. Production instead seeds SB-GRPC-PSK-<siteId> into the
+      # secret store, which is also the only source that can serve a site added at runtime.
+      ScadaBridge__Communication__SitePsks__site-a: "dev-grpc-psk-docker-site-a"
+      ScadaBridge__Communication__SitePsks__site-b: "dev-grpc-psk-docker-site-b"
+      ScadaBridge__Communication__SitePsks__site-c: "dev-grpc-psk-docker-site-c"
     ports:
       - "9002:5000"   # Web UI + Inbound API
       - "9012:8081"   # Akka remoting

docker/site-a-node-a/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-a",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"

docker/site-a-node-b/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-a",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"

docker/site-b-node-a/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-b",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"

docker/site-b-node-b/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-b",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"

docker/site-c-node-a/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-c",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"

docker/site-c-node-b/appsettings.Site.json

@@ -41,6 +41,13 @@
       "SqliteDbPath": "/app/data/store-and-forward.db"
     },
     "Communication": {
+      // DEV-ONLY control-plane preshared key — NOT a real secret. Must be
+      // IDENTICAL on both nodes of the pair and match the central-side entry in
+      // ScadaBridge__Communication__SitePsks__<siteId> (docker-compose.yml).
+      // Production supplies this as ${secret:SB-GRPC-PSK-<siteId>}. Without it the
+      // node fails StartupValidator: the gate is fail-closed, so an unset key would
+      // refuse every SiteStream call while the node still looked healthy.
+      "GrpcPsk": "dev-grpc-psk-docker-site-c",
       "CentralContactPoints": [
         "akka.tcp://scadabridge@scadabridge-central-a:8081",
         "akka.tcp://scadabridge@scadabridge-central-b:8081"