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/sim/dto/sim.dto.ts

@@ -0,0 +1,17 @@
+import { IsNotEmpty, IsString, MaxLength } from 'class-validator';
+import { MqttPointDto } from '../../ingest/dto/mqtt-messages.dto';
+
+// What the simulator UI sends the backend. Mirrors a devices/<serial>/log
+// payload plus the two fields that live in the topic/routing rather than the
+// wire payload itself (serial, jobId) so this DTO doubles as validation for
+// both the REST call and the outgoing MQTT message.
+export class SimPublishPointDto extends MqttPointDto {
+  @IsString()
+  @IsNotEmpty()
+  @MaxLength(64)
+  serial: string;
+
+  @IsString()
+  @IsNotEmpty()
+  jobId: string;
+}