Secondary SDR priority: every spare SDR runs the next decoder in an ordered list

Replaces the single secondary_sdr_mode with secondary_sdr_priority, e.g.
["adsb", "ais"]. OP25 always keeps its own dongle; the secondary-sdr
container starts decoders top-down until it runs out of free SDRs, so a
3-SDR node runs ADS-B and AIS at once and a 2-SDR node runs the top pick.

- secondary-sdr: one decoder per mode, POST /secondary/apply(priority)
  (no-op when the right prefix is already running), orphaned decoders
  from a uvicorn reload are reaped on start, /status reports sdr_count
  via lsusb (op25's :stable image has none).
- edge-node: one apply path (set_secondary_priority) for the local
  dashboard, a new C2 'set_secondary_priority' MQTT command, and config
  pushes; it never restarts op25. Legacy mode migrates on load. Checkin
  reports priority, what's running, and sdr_count. Uplink forwards
  aircraft and vessels whenever either is present.
- Local dashboard: 'Secondary SDRs' card to enable/reorder/save.

Verified: edge-node pytest 190 passed, flake8 clean.

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

drb-edge-node/tests/test_secondary_priority.py

@@ -0,0 +1,58 @@
+"""
+node-26#9 — secondary SDR priority: an ordered list the SDRs beyond op25's work
+through. Normalisation, migration from the legacy single-mode field, and the one
+apply path shared by the dashboard, C2 commands and config pushes.
+"""
+import asyncio
+from unittest.mock import AsyncMock, patch
+
+from app.models import NodeConfig, normalize_secondary_priority
+
+
+def _cfg(**kw) -> NodeConfig:
+    return NodeConfig(node_id="n1", node_name="N1", lat=0.0, lon=0.0, **kw)
+
+
+def test_normalize_keeps_order_drops_unknown_and_duplicates():
+    assert normalize_secondary_priority(["ais", "bogus", "adsb", "ais"]) == ["ais", "adsb"]
+    assert normalize_secondary_priority([]) == []
+
+
+def test_legacy_single_mode_migrates_to_priority():
+    assert _cfg(secondary_sdr_mode="adsb").secondary_sdr_priority == ["adsb"]
+    assert _cfg(secondary_sdr_mode="none").secondary_sdr_priority == []
+
+
+def test_explicit_priority_wins_over_legacy_mode():
+    assert _cfg(secondary_sdr_mode="adsb", secondary_sdr_priority=["ais"]).secondary_sdr_priority == ["ais"]
+
+
+def test_set_priority_persists_applies_and_never_touches_op25(tmp_path):
+    config_file = tmp_path / "node_config.json"
+    import app.internal.config_manager as cm
+    with patch.object(cm, "_CONFIG_FILE", config_file):
+        cm.save_node_config(_cfg(secondary_sdr_mode="adsb"))
+        from app.internal import secondary_priority as sp
+        with patch.object(sp.secondary_sdr_client, "apply", AsyncMock(return_value=["ais"])) as apply, \
+             patch("app.internal.mqtt_manager.mqtt_manager.publish_checkin", AsyncMock()), \
+             patch("app.internal.op25_client.op25_client.stop", AsyncMock()) as op25_stop:
+            running = asyncio.run(sp.set_secondary_priority(["ais", "adsb", "ais"]))
+        saved = cm.load_node_config()
+
+    assert running == ["ais"]
+    apply.assert_awaited_once_with(["ais", "adsb"])
+    op25_stop.assert_not_awaited()
+    assert saved.secondary_sdr_priority == ["ais", "adsb"]
+    assert saved.secondary_sdr_mode == "ais"
+
+
+def test_clearing_priority_is_not_undone_by_legacy_migration(tmp_path):
+    config_file = tmp_path / "node_config.json"
+    import app.internal.config_manager as cm
+    with patch.object(cm, "_CONFIG_FILE", config_file):
+        cm.save_node_config(_cfg(secondary_sdr_mode="adsb"))
+        from app.internal import secondary_priority as sp
+        with patch.object(sp.secondary_sdr_client, "apply", AsyncMock(return_value=[])), \
+             patch("app.internal.mqtt_manager.mqtt_manager.publish_checkin", AsyncMock()):
+            asyncio.run(sp.set_secondary_priority([]))
+        assert cm.load_node_config().secondary_sdr_priority == []