Wire AIS end to end: AIS-catcher support in secondary-sdr container

node-26#9. decoder_control.py's AIS mode now actually launches AIS-catcher
instead of 400ing: a background thread reads its stdout JSON stream
(one message per line) and keeps a live in-memory snapshot keyed by mmsi,
since AIS-catcher streams rather than writing a periodic file the way
dump1090's --write-json does. Messages are merged onto the existing entry
per mmsi rather than replacing it, since AIS-catcher emits static data
(name) and position reports (lat/lon) as separate message types — a naive
overwrite would blank the name back to null on every position-only update
(caught by a standalone unit check against a fake stdout stream before
this fix, not by pytest — this container has no test suite yet).

edge-node's telemetry_uplink_loop now posts non-empty vessel snapshots to
the new /telemetry/ais the same way it already does for aircraft.

UNVERIFIED against real hardware/binary in this session, same caveat as
the ADS-B commit — AIS-catcher's JSON field names are believed correct
from its docs, not confirmed against a real capture.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

drb-edge-node/app/internal/telemetry_uplink.py

@@ -33,9 +33,12 @@ async def telemetry_uplink_loop():
     while True:
         await asyncio.sleep(UPLINK_INTERVAL_SECONDS)
         config = load_node_config()
-        if config.secondary_sdr_mode != "adsb":
+        if config.secondary_sdr_mode not in ("adsb", "ais"):
             continue
         snapshot = await secondary_sdr_client.data()
-        if not snapshot or not snapshot.get("aircraft"):
+        if not snapshot:
             continue
-        await _post_snapshot("/telemetry/adsb", {"aircraft": snapshot["aircraft"]})
+        if config.secondary_sdr_mode == "adsb" and snapshot.get("aircraft"):
+            await _post_snapshot("/telemetry/adsb", {"aircraft": snapshot["aircraft"]})
+        elif config.secondary_sdr_mode == "ais" and snapshot.get("vessels"):
+            await _post_snapshot("/telemetry/ais", {"vessels": snapshot["vessels"]})