Add GET /api/channels, move endpoints under /api prefix, serve Scalar docs at / (issue #1)

- New GET /api/channels: device Meshtastic channels from FromRadio.channel
  frames during initial sync; psk/keys redacted; map reset on reconnect.
- app.setGlobalPrefix('api'): /status -> /api/status, /send -> /api/send.
- Scalar API docs at / (OpenAPI JSON at /docs-json) via @nestjs/swagger +
  @scalar/nestjs-api-reference; light swagger decorators on endpoints/body.
- MESH_RECONNECT_MS env knob (default 5000 ms).
- v0.1.0: CHANGELOG entry, README/AGENTS/ORCHESTRATOR docs sync.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "mesh-bot",
-  "version": "0.0.1",
+  "version": "0.1.0",
   "description": "",
   "author": "",
   "private": true,
@@ -26,6 +26,8 @@
     "@nestjs/common": "^12.0.1",
     "@nestjs/core": "^12.0.1",
     "@nestjs/platform-express": "^12.0.1",
+    "@nestjs/swagger": "^12.0.2",
+    "@scalar/nestjs-api-reference": "^1.2.21",
     "reflect-metadata": "^0.2.2",
     "rxjs": "^7.8.1"
   },