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>

op25-container/tests/test_conventional.py

@@ -149,6 +149,23 @@ def test_generate_config_route(tmp_path, monkeypatch):
     cfg = json.loads((tmp_path / "active.cfg.json").read_text())
     assert cfg["trunking"]["module"] == "tk_drb_conv.py"
     assert cfg["channels"][0]["frequency"] == 154430000
+    # node-26#46: analog defaults to OP25's noise squelch, not power.
+    assert cfg["channels"][0]["nbfm_squelch_mode"] == "noise"
+    assert "nbfm_noise_squelch_db" not in cfg["channels"][0]
+
+    r = client.post("/op25/generate-config", json={
+        "type": "NBFM", "systemName": "Fire", "channels": [154430000], "icecastConfig": ice,
+        "nbfm_squelch_mode": "power", "nbfm_squelch": -55, "nbfm_noise_squelch_db": 12,
+    })
+    assert r.status_code == 200, r.text
+    ch = json.loads((tmp_path / "active.cfg.json").read_text())["channels"][0]
+    assert ch["nbfm_squelch_mode"] == "power" and ch["nbfm_squelch_threshold"] == -55
+    assert ch["nbfm_noise_squelch_db"] == 12
+
+    r = client.post("/op25/generate-config", json={
+        "type": "NBFM", "systemName": "Fire", "channels": [154430000], "nbfm_squelch_mode": "loud",
+    })
+    assert r.status_code == 422
 
 
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