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-frontend/lib/types.ts

@@ -58,6 +58,12 @@ export interface NodeRecord {
   secondary_sdr_priority?: string[];
   /** What the node's last checkin reported actually running. */
   secondary_sdr_running?: string[] | null;
+  /** node-26#11: service (op25/adsb/ais) -> dongle serial; absent = automatic. */
+  sdr_pins?: Record<string, string>;
+  /** Dongles the node detected, from its checkin; null/absent = not reported. */
+  sdr_devices?: SdrDevice[] | null;
+  /** The dongle OP25 is actually using, per the node. */
+  op25_sdr_serial?: string | null;
   sdr_count?: number | null; // null = never reported
   enforce_override_timeout?: boolean;
   is_overridden?: boolean;
@@ -65,6 +71,13 @@ export interface NodeRecord {
   override_timeout_at?: string | null;
 }
 
+export interface SdrDevice {
+  index: number;
+  serial: string | null;
+  name: string;
+  duplicate_serial: boolean;
+}
+
 export interface AircraftTrack {
   icao: string;
   org_id?: string;