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/sdr_settings.py

@@ -0,0 +1,102 @@
+"""
+Which SDR does what on this node (node-26#9, node-26#11).
+
+- OP25 always has exactly one dongle. `sdr_pins["op25"]` names it by serial;
+  unpinned, OP25 keeps its historical "first dongle" — but that dongle is now
+  named by serial too, so the decoders can never take it out from under OP25.
+- Every other dongle runs the next enabled service in `secondary_sdr_priority`.
+  `sdr_pins[mode]` optionally binds a service to the dongle carrying its
+  antenna; unpinned services take any spare.
+
+One apply path for the local dashboard, C2 commands and config pushes.
+"""
+import asyncio
+import json
+from pathlib import Path
+from typing import Any, Dict, Iterable, List, Optional
+
+from app.config import settings
+from app.internal.config_manager import load_node_config, save_node_config
+from app.internal.logger import logger
+from app.internal.secondary_sdr_client import secondary_sdr_client
+from app.models import NodeConfig, normalize_sdr_pins, normalize_secondary_priority
+
+_OP25_CONFIG = Path(settings.config_path) / "active.cfg.json"
+
+
+def op25_serial(cfg: NodeConfig, devs: Optional[List[Dict[str, Any]]]) -> Optional[str]:
+    """The serial of OP25's dongle: the pin, else the first detected dongle
+    (what OP25's plain "rtl" device string has always opened)."""
+    if cfg.sdr_pins.get("op25"):
+        return cfg.sdr_pins["op25"]
+    return devs[0]["serial"] if devs else None
+
+
+async def pin_op25_device() -> Optional[str]:
+    """Rewrite OP25's generated config to open its dongle by serial.
+
+    Runs after every generate-config (op25_client.generate_config). A plain
+    "rtl" means "device 0", and which dongle is device 0 depends on who opened
+    what first — that is how OP25 lost its SDR to readsb on 2026-09-27.
+    Left as "rtl" only when the serial is unknown or shared by two dongles.
+    """
+    devs = await secondary_sdr_client.devices()
+    serial = op25_serial(load_node_config(), devs)
+    if not serial or (devs and sum(d["serial"] == serial for d in devs) > 1):
+        return None
+    try:
+        cfg = json.loads(_OP25_CONFIG.read_text())
+        for dev in cfg.get("devices", []):
+            dev["args"] = f"rtl={serial}"
+        _OP25_CONFIG.write_text(json.dumps(cfg, indent=2))
+    except Exception as e:
+        logger.error(f"Could not pin OP25 to SDR {serial}: {e}")
+        return None
+    return serial
+
+
+async def apply_secondaries() -> Optional[List[str]]:
+    """Start/stop decoders to match the saved priority and pins, never on OP25's dongle."""
+    cfg = load_node_config()
+    if not cfg.secondary_sdr_priority:
+        return await secondary_sdr_client.apply([], {}, [])
+    devs = await secondary_sdr_client.devices()
+    reserved = [s for s in [op25_serial(cfg, devs)] if s]
+    pins = {m: s for m, s in cfg.sdr_pins.items() if m != "op25"}
+    return await secondary_sdr_client.apply(cfg.secondary_sdr_priority, pins, reserved)
+
+
+async def set_sdr_settings(priority: Optional[Iterable[str]] = None,
+                           pins: Optional[Dict[str, Optional[str]]] = None) -> Optional[List[str]]:
+    """Persist and apply priority and/or pins. OP25 restarts only if its own
+    dongle changed; reordering the spare dongles never interrupts P25.
+
+    Returns the decoders now running (None if the container is unreachable).
+    """
+    cfg = load_node_config()
+    old_op25 = cfg.sdr_pins.get("op25")
+    if priority is not None:
+        ordered = normalize_secondary_priority(priority)
+        cfg.secondary_sdr_priority = ordered
+        cfg.secondary_sdr_mode = ordered[0] if ordered else "none"
+    if pins is not None:
+        cfg.sdr_pins = normalize_sdr_pins(pins)
+    save_node_config(cfg)
+
+    if cfg.sdr_pins.get("op25") != old_op25:
+        from app.internal.op25_client import op25_client
+        # Free the new dongle first if a decoder holds it, then move OP25.
+        await secondary_sdr_client.apply([], {}, [])
+        serial = await pin_op25_device()
+        await op25_client.stop()
+        await asyncio.sleep(2)
+        await op25_client.start()
+        logger.info(f"OP25 moved to SDR {serial or 'rtl (first dongle)'}")
+
+    running = await apply_secondaries()
+    logger.info(f"SDR settings: priority={cfg.secondary_sdr_priority!r} pins={cfg.sdr_pins!r}; running {running!r}")
+
+    # Report straight away so C2's view doesn't wait for the next heartbeat.
+    from app.internal.mqtt_manager import mqtt_manager
+    asyncio.create_task(mqtt_manager.publish_checkin())
+    return running