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/talkgroups.py

@@ -44,7 +44,10 @@ async def name_from_system(system_id: Optional[str], talkgroup_id: Optional[int]
                 return tg.get("name") or None
         except (TypeError, ValueError):
             continue
-    return None
+    # A conventional/analog call labelled with its channel's synthetic id
+    # (frequency in 100 Hz units, node-26#24) is named after the channel.
+    from app.internal.system_config import conventional_channel_name
+    return conventional_channel_name(system_doc, tgid_int)
 
 
 async def resolve(