Add live transmitter position (status) alongside logged points

devices/<serial>/log messages now carry a "type": "log" or "status".
"log" persists a LocatePoint as before; "status" carries the same
position + telemetry shape but is broadcast live over the job's
realtime channel without touching locate_points — it's a current-
position update, not a recorded point.

The job map renders the latest status as a blue "you are here" marker
(with a soft accuracy-radius halo) that moves in place as new updates
arrive, separate from the colored polyline of logged points. Clicking
it shows the same detail readout as a logged point.

The simulator gained a message-type toggle (Log point / Status
update) so both paths can be exercised from /sim.

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

backend/src/sim/dto/sim.dto.ts

@@ -1,17 +1,12 @@
 import { IsNotEmpty, IsString, MaxLength } from 'class-validator';
-import { MqttPointDto } from '../../ingest/dto/mqtt-messages.dto';
+import { MqttLogMessageDto } 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 {
+// What the simulator UI sends the backend: a devices/<serial>/log payload
+// (type: "log" persists a point, "status" is a live-only position update)
+// plus "serial", which lives in the topic rather than the wire payload.
+export class SimPublishPointDto extends MqttLogMessageDto {
   @IsString()
   @IsNotEmpty()
   @MaxLength(64)
   serial: string;
-
-  @IsString()
-  @IsNotEmpty()
-  jobId: string;
 }