Pin each SDR service to a dongle by serial; OP25 always opens its SDR by serial

Fixes node-26#11. OP25's generated config said "rtl" (= whichever dongle
enumerates first), so on 2-SDR nodes a decoder could take OP25's dongle
and stop recording. Now:

- sdr_pins: {op25|adsb|ais: serial}, absent = automatic. Every OP25
  config generation (op25_client.generate_config) rewrites the device to
  rtl=<serial>: the pin, else the first dongle's serial, which is what
  "rtl" always opened. Left as "rtl" only for unknown/shared serials.
- secondary-sdr: /secondary/devices lists dongles + serials via librtlsdr
  (works while claimed). apply(priority, pins, reserved) never touches
  OP25's dongle, gives a pinned service only its own dongle, lets a
  higher-priority service take a spare from a lower one, and still runs a
  pinned lower-priority service when the top pick has no dongle.
- sdr_settings.py replaces secondary_priority.py: one apply path for the
  local dashboard, the new set_sdr_config C2 command (set_secondary_priority
  kept as an alias) and config pushes. OP25 restarts only when its own
  dongle changes. Checkin reports sdr_devices, sdr_pins, op25_sdr_serial.
- Local dashboard: 'SDRs' card with an OP25 SDR dropdown and a per-service
  dongle dropdown, duplicate-serial and double-pin warnings.

Verified: edge-node pytest 194 passed; secondary-sdr tests 7 passed;
flake8 clean; page JS passes node --check.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

secondary-sdr-container/app/routers/secondary_controller.py

@@ -1,4 +1,4 @@
-from typing import List, Optional
+from typing import Dict, List, Optional
 
 from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel
@@ -19,6 +19,8 @@ class StopBody(BaseModel):
 
 class ApplyBody(BaseModel):
     priority: List[str]  # ordered, e.g. ["adsb", "ais"]
+    pins: Dict[str, str] = {}  # mode -> serial of the dongle with its antenna
+    reserved: List[str] = []  # serials no decoder may touch (op25's)
 
 
 def create_secondary_router():
@@ -27,7 +29,7 @@ def create_secondary_router():
     @router.post("/apply")
     async def apply(body: ApplyBody):
         try:
-            live = decoder_control.apply(body.priority)
+            live = decoder_control.apply(body.priority, body.pins, body.reserved)
         except ValueError as e:
             raise HTTPException(status_code=400, detail=str(e))
         return {"running": live}
@@ -51,6 +53,10 @@ def create_secondary_router():
     async def get_status():
         return decoder_control.status()
 
+    @router.get("/devices")
+    async def get_devices():
+        return {"devices": decoder_control.devices()}
+
     @router.get("/data")
     async def get_data():
         return decoder_control.data()