Systems: P25 trunked / P25 conventional / analog as one choice (node-26#24)

- system_config.normalize(): a P25 system with config.mode "conventional"
  carries config.channels [{freq MHz, name, nac?}] (1-2, within 1.5 MHz) and
  can no longer carry control channels (422). A missing mode is trunked and
  passes through untouched, so there is no migration. An analog channel is
  mirrored into control_channels for older nodes.
- talkgroups.name_from_system resolves the edge node's synthetic per-channel
  id (freq in 100 Hz units) to the channel name.
- The checkin persists radio_channels (conventional channels + encryption).
- Systems editor: Type = P25 trunked / P25 conventional / Analog (NBFM) /
  DMR, plus a channel-row editor for conventional and a one-frequency form for
  analog. The node page shows conventional channels and an encryption notice.

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

drb-c2-core/app/internal/mqtt_handler.py

@@ -148,8 +148,11 @@ class MQTTHandler:
             updates["node_type"] = node_type
             updates["enforce_override_timeout"] = enforce_timeout
 
+            # radio_channels (node-26#24): a conventional node's channels and
+            # whether each is encrypted — the one decode failure the owner has
+            # to hear about from C2, since nothing on the node can fix it.
             for key in ("secondary_sdr_mode", "secondary_sdr_priority", "secondary_sdr_running",
-                        "sdr_pins", "sdr_devices", "op25_sdr_serial"):
+                        "sdr_pins", "sdr_devices", "op25_sdr_serial", "radio_channels"):
                 if key in payload:
                     updates[key] = payload[key]
             if "sdr_count" in payload: