Tie points to locator serial numbers and store receiver telemetry

Adds devices/<serial>/log as a job-anchored MQTT ingest path: a locator
identifies itself by serial in the topic (auto-registered on first
sight, org resolved from the job in the payload) rather than by a
pre-provisioned broker credential. Device.serialNumber is now globally
unique so the bare topic segment is enough to resolve identity.
Locator lookup/auto-register logic is shared (LocatorRegistryService)
between this and the existing devices/<mqttUsername>/points path.

New /sim page (own header, outside the main app nav) simulates a
transmitter: pick an open job or create one, set a serial number and
telemetry defaults, and send points one at a time or on an interval
along a simulated walking path. It calls a new authenticated backend
endpoint (POST /orgs/:orgId/sim/publish) that publishes onto the real
broker rather than writing the DB directly, so the simulator exercises
the actual ingest pipeline end-to-end.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/app.module.ts

@@ -11,6 +11,7 @@ import { DevicesModule } from './devices/devices.module';
 import { IngestModule } from './ingest/ingest.module';
 import { RealtimeModule } from './realtime/realtime.module';
 import { ApiKeysModule } from './api-keys/api-keys.module';
+import { SimModule } from './sim/sim.module';
 
 @Module({
   imports: [
@@ -23,6 +24,7 @@ import { ApiKeysModule } from './api-keys/api-keys.module';
     IngestModule,
     RealtimeModule,
     ApiKeysModule,
+    SimModule,
   ],
   controllers: [AppController, StatusController],
   providers: [AppService],