Node SDRs: pin OP25 and each service to a dongle by serial (node-26#11)

Pairs with node-26 feat/sdr-pins. NodeRecord gains sdr_pins
(service -> serial), sdr_devices and op25_sdr_serial, mirrored from the
node's checkin. PATCH /nodes/{id} validates pins (known services, one
dongle per service) and sends priority/pins as a 'set_sdr_config'
command, never a config re-push. The node restarts OP25 only when OP25's
own dongle changes. The node page's section becomes 'SDRs' with an OP25
SDR dropdown ('Automatic (first SDR)' + detected dongles) and a
per-service dongle dropdown ('Any spare SDR'), plus duplicate-serial and
double-pin warnings.

Verified: c2-core pytest 490 passed; frontend tsc --noEmit clean.

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

drb-c2-core/tests/test_node_secondary_priority.py

@@ -40,7 +40,7 @@ def _patch(body):
 def test_priority_only_sends_command_and_never_repushes_config():
     resp, update, command, push = _patch({"secondary_sdr_priority": ["ais", "adsb"]})
     assert resp.status_code == 200
-    command.assert_called_once_with("n1", {"action": "set_secondary_priority", "priority": ["ais", "adsb"]})
+    command.assert_called_once_with("n1", {"action": "set_sdr_config", "priority": ["ais", "adsb"]})
     push.assert_not_called()
     (_, _, updates), _ = update.await_args
     assert updates == {"secondary_sdr_priority": ["ais", "adsb"], "secondary_sdr_mode": "ais"}
@@ -49,7 +49,7 @@ def test_priority_only_sends_command_and_never_repushes_config():
 def test_empty_priority_turns_secondaries_off():
     resp, update, command, push = _patch({"secondary_sdr_priority": []})
     assert resp.status_code == 200
-    command.assert_called_once_with("n1", {"action": "set_secondary_priority", "priority": []})
+    command.assert_called_once_with("n1", {"action": "set_sdr_config", "priority": []})
     (_, _, updates), _ = update.await_args
     assert updates["secondary_sdr_mode"] == "none"
 
@@ -57,3 +57,20 @@ def test_empty_priority_turns_secondaries_off():
 def test_unknown_or_duplicate_modes_are_rejected():
     assert _patch({"secondary_sdr_priority": ["adsb", "sonar"]})[0].status_code == 400
     assert _patch({"secondary_sdr_priority": ["adsb", "adsb"]})[0].status_code == 400
+
+
+def test_pins_send_every_service_with_nulls_for_automatic():
+    resp, update, command, push = _patch({"sdr_pins": {"op25": "00000001", "adsb": "69420", "ais": ""}})
+    assert resp.status_code == 200
+    push.assert_not_called()
+    command.assert_called_once_with("n1", {
+        "action": "set_sdr_config",
+        "pins": {"op25": "00000001", "adsb": "69420", "ais": None},
+    })
+    (_, _, updates), _ = update.await_args
+    assert updates == {"sdr_pins": {"op25": "00000001", "adsb": "69420"}}
+
+
+def test_two_services_on_one_dongle_or_unknown_service_rejected():
+    assert _patch({"sdr_pins": {"op25": "69420", "adsb": "69420"}})[0].status_code == 400
+    assert _patch({"sdr_pins": {"sonar": "1"}})[0].status_code == 400