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>

drb-edge-node/app/internal/op25_client.py

@@ -80,10 +80,14 @@ class OP25Client:
             async with httpx.AsyncClient(timeout=10) as client:
                 r = await client.post(f"{self.api_url}/op25/generate-config", json=config)
                 r.raise_for_status()
-                return True
         except Exception as e:
             logger.error(f"OP25 generate-config failed: {e}")
             return False
+        # Every generated config opens its dongle by serial, never "first
+        # found" (node-26#11) — here so no generation path can skip it.
+        from app.internal.sdr_settings import pin_op25_device
+        await pin_op25_device()
+        return True
 
     async def poll_terminal(self) -> Optional[TerminalUpdate]:
         """