fix(archreview): security authz+hub cluster (SEC-07/05/08/11) + validation hardening

SEC-07: add QueryActiveAlarmsRequest -> events:read scope arm; fix two tests that
  constructed StreamAlarmsRequest instead of QueryActiveAlarmsRequest.
SEC-05: shorten hub-token lifetime 30m -> 5m; document that the ?access_token= query
  carriage must never be request-logged.
SEC-08: gateway-side CachingApiKeyVerifier (short TTL, keyed on a hash of the presented
  secret) skips the per-call store read+last_used write; CoalescingMarkApiKeyStore bounds
  last_used writes to <=1/key/min; identity constraints are cached. Invalidation is wired
  at the gateway admin sites (revoke/rotate/delete); short TTL backstops out-of-process CLI.
SEC-11: fixed-window rate limit on POST /auth/login + a per-peer (key-id) failure limiter
  checked before VerifyAsync; new MxGateway:Security options bound + validated.

Also fixes regressions from the SEC-01/04/06 commit (c185f62) that a narrow test filter
missed (all now covered by a full-suite checkpoint):
- Rooting check is cross-platform: accepts Windows C:\/UNC forms on Unix so the shipped
  appsettings path validates on the macOS dev box, still rejecting bare filenames.
- AddGatewayConfiguration TryAdds a non-production IHostEnvironment fallback so the validator
  resolves in minimal test/tooling containers; the real host + apikey CLI register the actual
  environment first (TryAdd no-op there).
- Test assembly defaults ASPNETCORE_ENVIRONMENT=Development (ModuleInitializer) so full-host
  tests exercise wiring instead of tripping the SEC-04/06 production guards.
- GatewayOptionsTests asserts the SEC-01 CommonApplicationData-derived default (platform-correct).

archreview: SEC-07/05/08/11 (P1). Verified: NonWindows build clean; full gateway suite
747 passed / 42 failed, where all 42 are the pre-existing macOS named-pipe-harness failures
(Unix-socket path limit) and 0 are validation/regression failures.

docs/Authorization.md

@@ -89,6 +89,12 @@ The flow is:
 
 The status codes are deliberately distinct: `Unauthenticated` signals "we do not know who you are," and `PermissionDenied` signals "we know who you are, but you cannot do this." Treating the two as the same code would make troubleshooting harder for client implementations.
 
+### Rate limiting the auth surface (SEC-11)
+
+Before the verification store read, the helper checks a cheap in-process per-peer failure counter (`ApiKeyFailureLimiter`). A peer that has accumulated more than `MxGateway:Security:ApiKeyFailureLimit` failed attempts inside the sliding `ApiKeyFailureWindowSeconds` window is short-circuited with `StatusCode.ResourceExhausted` — so online guessing of API-key secrets cannot spend a SQLite read (and, in a naive design, a cache miss) per attempt. The peer is keyed on the presented key id where the token parses, falling back to the transport peer address; keying on key id throttles a single abusive credential without penalizing co-located clients behind a shared NAT. A successful verification resets the peer's counter. The counter is a bounded LRU (`ApiKeyFailureTrackedPeers`) so it cannot grow without limit. `ResourceExhausted` reveals only that throttling is in effect, not whether any particular secret was valid, preserving the opaque-failure property.
+
+The dashboard login surface is throttled independently: `POST /auth/login` carries a fixed-window ASP.NET Core rate-limiter policy keyed per remote IP (`MxGateway:Security:LoginRateLimit*`), rejecting a burst with HTTP 429 before the LDAP bind is relayed to the directory. See [GatewayConfiguration](./GatewayConfiguration.md#security-options).
+
 ## Scope Resolution
 
 `GatewayGrpcScopeResolver` is a stateless singleton that switches on the runtime request type. Top-level RPC requests map directly:
@@ -104,6 +110,7 @@ public string ResolveRequiredScope(object request)
         MxCommandRequest commandRequest => ResolveCommandScope(commandRequest.Command?.Kind ?? MxCommandKind.Unspecified),
         AcknowledgeAlarmRequest => GatewayScopes.InvokeWrite,
         StreamAlarmsRequest => GatewayScopes.EventsRead,
+        QueryActiveAlarmsRequest => GatewayScopes.EventsRead,
         TestConnectionRequest or
         GetLastDeployTimeRequest or
         DiscoverHierarchyRequest or
@@ -113,7 +120,7 @@ public string ResolveRequiredScope(object request)
 }
 ```
 
-The `_ => GatewayScopes.Admin` fallback is intentional: any future request type that the resolver does not recognize fails closed, requiring the strongest scope until the resolver is updated. `AcknowledgeAlarm` is treated as a write — it mutates alarm state, mirroring `MxCommandKind.Write*` — and `StreamAlarms` shares the alarm/event surface with `StreamEvents` and `MxCommandKind.DrainEvents`, so it carries `events:read`. Both alarm RPCs are session-less: the scope check is the only authorization gate, since there is no per-session ownership to enforce.
+The `_ => GatewayScopes.Admin` fallback is intentional: any future request type that the resolver does not recognize fails closed, requiring the strongest scope until the resolver is updated. `AcknowledgeAlarm` is treated as a write — it mutates alarm state, mirroring `MxCommandKind.Write*` — and `StreamAlarms` and `QueryActiveAlarms` share the alarm/event surface with `StreamEvents` and `MxCommandKind.DrainEvents`, so they carry `events:read` (the active-alarm snapshot is the same data reachable through the event surface). All three alarm RPCs are session-less: the scope check is the only authorization gate, since there is no per-session ownership to enforce.
 
 `MxCommandRequest` is special because it multiplexes many MxAccess operations through a single RPC. The resolver inspects the embedded `MxCommandKind` so each operation gets its own scope:
 
@@ -205,7 +212,7 @@ blocking constraint; secured values and raw credentials are never logged.
 |----------|-------|--------------|
 | `SessionOpen` | `session:open` | `OpenSessionRequest` |
 | `SessionClose` | `session:close` | `CloseSessionRequest` |
-| `EventsRead` | `events:read` | `StreamEventsRequest`, `StreamAlarmsRequest`, `MxCommandKind.DrainEvents` |
+| `EventsRead` | `events:read` | `StreamEventsRequest`, `StreamAlarmsRequest`, `QueryActiveAlarmsRequest`, `MxCommandKind.DrainEvents` |
 | `InvokeRead` | `invoke:read` | `MxCommandRequest` for read-style command kinds (`Register`, `AddItem`, `Advise`, `ReadBulk`, and any kind not otherwise mapped) |
 | `InvokeWrite` | `invoke:write` | `AcknowledgeAlarmRequest`, `MxCommandKind.Write`, `MxCommandKind.Write2`, `MxCommandKind.WriteBulk`, `MxCommandKind.Write2Bulk` |
 | `InvokeSecure` | `invoke:secure` | `MxCommandKind.WriteSecured`, `MxCommandKind.WriteSecured2`, `MxCommandKind.WriteSecuredBulk`, `MxCommandKind.WriteSecured2Bulk`, `MxCommandKind.AuthenticateUser` |