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/GatewayConfiguration.md

@@ -218,9 +218,13 @@ When the dashboard is enabled, three hubs are mapped under `/hubs/*`:
   side-effect; the dashboard only sees events while a gRPC client is also
   subscribed to that session.
 
-`GET /hubs/token` (cookie-only) mints a 30-minute data-protected bearer
+`GET /hubs/token` (cookie-only) mints a 5-minute data-protected bearer
 token for the calling user; the Blazor pages use it via
 `DashboardHubConnectionFactory` to authenticate the SignalR connection.
+The factory refreshes the token on every (re)connect, so the short lifetime
+(SEC-05) is transparent to clients. The token is not server-side revocable;
+its short lifetime bounds exposure of a captured token (see
+[GatewayDashboardDesign](./GatewayDashboardDesign.md)).
 
 ## LDAP Options (Dashboard Login)
 
@@ -258,6 +262,23 @@ The protocol option is exposed for diagnostics and explicit deployment
 configuration, not for compatibility negotiation. A mismatch fails validation
 at startup.
 
+## Security Options
+
+Bound from `MxGateway:Security`. These knobs tune the authentication hot path
+(SEC-08 verification cache / last-used coalescing) and the auth-surface rate
+limiting (SEC-11). Defaults are safe; leave them unless profiling or a threat
+model requires otherwise.
+
+| Option | Default | Description |
+|--------|---------|-------------|
+| `MxGateway:Security:ApiKeyVerificationCacheSeconds` | `15` | TTL, in seconds, of a cached successful API-key verification. A cache hit within this window skips the per-call SQLite read (and the coupled `last_used` write). Gateway-initiated revoke/rotate/delete invalidate the entry immediately; this TTL is the backstop for out-of-band mutations (a direct DB edit, or a revoke run by the separate `apikey` CLI process). `0` disables the cache. Must be zero or greater. |
+| `MxGateway:Security:ApiKeyLastUsedCoalesceSeconds` | `60` | Coalescing window, in seconds, for the `last_used_utc` write. The library verifier writes `last_used` on every successful verification; this bounds the write to at most one per key per window, so a hammered key does not churn the WAL. `0` forwards every write. Must be zero or greater. |
+| `MxGateway:Security:LoginRateLimitPermitLimit` | `10` | Maximum `POST /auth/login` attempts permitted per remote IP within `LoginRateLimitWindowSeconds` before requests are rejected with HTTP 429. Throttles LDAP credential stuffing before the bind is relayed to the directory. Must be greater than zero. |
+| `MxGateway:Security:LoginRateLimitWindowSeconds` | `60` | Fixed-window length, in seconds, for the per-IP login rate limit. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureLimit` | `10` | Failed API-key verifications, per peer, within `ApiKeyFailureWindowSeconds` that trip the in-process short-circuit. Once tripped, the gRPC auth path rejects further attempts with `ResourceExhausted` **before** the store read; a successful verification resets the peer's counter. The peer is keyed on the presented key id (falling back to the transport address) so a single abusive credential behind a shared NAT is throttled without locking out co-located clients. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureWindowSeconds` | `60` | Sliding-window length, in seconds, over which API-key verification failures are counted per peer. Must be greater than zero. |
+| `MxGateway:Security:ApiKeyFailureTrackedPeers` | `4096` | Maximum distinct peers tracked by the failure counter (a bounded LRU) so a spray of unique peer keys cannot grow memory without limit. Must be greater than zero. |
+
 ## Galaxy Options
 
 | Option | Default | Description |