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_conventional.py

@@ -78,6 +78,17 @@ def test_analog_payload_reads_channels_or_legacy(cfg):
     p = rc.build_generate_payload("NBFM", "Fire", cfg, ICE, "rtl-sdr-v3", None)
     assert p["channels"] == [154_430_000]
     assert "p25_mode" not in p
+    assert p["nbfm_squelch_mode"] == "noise"   # node-26#46 default
+
+
+def test_analog_squelch_is_plumbed_and_validated():
+    cfg = {"channels": [{"freq": 154.43}], "squelch_mode": "Power", "squelch_threshold": "-55", "squelch_db": 12}
+    p = rc.build_generate_payload("NBFM", "Fire", cfg, ICE, "rtl-sdr-v3", None)
+    assert p["nbfm_squelch_mode"] == "power" and p["nbfm_squelch"] == -55.0 and p["nbfm_noise_squelch_db"] == 12.0
+    with pytest.raises(ValueError):
+        rc.analog_squelch({"squelch_mode": "loud"})
+    with pytest.raises(ValueError):
+        rc.analog_squelch({"squelch_db": "lots"})
 
 
 def test_system_mode():