Add device-certificate mTLS auth, live position tracking, and API docs

Introduces a CA/PKI module so field devices can authenticate to Mosquitto
over TLS (8883) with per-device client certificates (CN = serial number)
instead of a shared password, with matching Devices/MQTT-Certs UI. Adds
live transmitter position tracking alongside logged points, an MQTTS
transport option in the simulator for exercising the real cert-auth path,
and Swagger API docs at /api/docs.

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

backend/nest-cli.json

@@ -1,4 +1,7 @@
 {
   "collection": "@nestjs/schematics",
-  "sourceRoot": "src"
+  "sourceRoot": "src",
+  "compilerOptions": {
+    "plugins": ["@nestjs/swagger"]
+  }
 }