op25: pin gr310 to 5b58335; analog defaults to OP25 noise squelch (node-26#46, node-26#29)

- op25-container/Dockerfile: clone gr310 then check out 5b58335 (OP25_COMMIT
  build arg). That is the gr310 merge tk_drb_conv was verified against for
  #29 and the first carrying PR #296's NBFM noise/voice squelch. Changing
  the RUN line also busts CI's cached unpinned clone.
- Keys verified from op25_nbfm.py at that commit: nbfm_squelch_mode
  (power|noise|voice), nbfm_noise_squelch_db, nbfm_squelch_threshold, read
  from the channel dict.
- op25-container: ConfigGenerator.nbfm_squelch_mode (enum, default noise) and
  nbfm_noise_squelch_db, written onto the analog channel.
- edge-node: system config squelch_mode / squelch_db / squelch_threshold ->
  generate payload (validated, noise when absent); /api/listen and the
  dashboard's analog pane expose mode and level.

#29's CI test of tk_drb_conv against the real tk_p25.py is not done here.

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

drb-edge-node/tests/test_local_dashboard.py

@@ -229,6 +229,17 @@ def test_listen_analog_single_frequency(client, op25):
     assert r.status_code == 200, r.text
     cfg = config_manager.load_node_config().override_config
     assert (cfg.type, cfg.name, cfg.config["control_channels"]) == ("NBFM", "Fire", [154.43])
+    assert cfg.config["squelch_mode"] == "noise"   # node-26#46 default
+
+
+def test_listen_analog_squelch_is_saved(client, op25):
+    r = client.post("/api/listen", json={"mode": "analog", "frequencies": [154.43],
+                                         "squelch_mode": "power", "squelch_threshold": -55})
+    assert r.status_code == 200, r.text
+    cfg = config_manager.load_node_config().override_config.config
+    assert (cfg["squelch_mode"], cfg["squelch_threshold"]) == ("power", -55)
+    assert client.post("/api/listen", json={"mode": "analog", "frequencies": [154.43],
+                                            "squelch_mode": "loud"}).status_code == 422
 
 
 def test_listen_p25_conventional(client, op25):