Releases: tag each healthy deploy vMAJOR.MINOR.PATCH; /health and node checkin report versions (node-26#49)

VERSION holds MAJOR.MINOR (1.1). The build job works out the next patch
(scripts/next-version.sh, integer count) and stamps it into c2-core as
DRB_VERSION, which /health returns. The new "Tag release" job tags the
commit only after the deploy job succeeds, so a failed deploy's number is
reused. Node checkins carry `version`, stored on the node doc.

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

drb-c2-core/app/internal/mqtt_handler.py

@@ -131,6 +131,7 @@ class MQTTHandler:
                 "sdr_count": payload.get("sdr_count"),  # None until reported, never a guessed 1
                 "disk_free_bytes": payload.get("disk_free_bytes"),
                 "disk_total_bytes": payload.get("disk_total_bytes"),
+                "version": payload.get("version"),  # installed release (node-26#49)
                 "enforce_override_timeout": payload.get("enforce_override_timeout", True),
                 "is_overridden": False,
                 "override_system_id": None,
@@ -168,7 +169,7 @@ class MQTTHandler:
             # records to — a full disk silently stopped node-002 for 17 days.
             for key in ("secondary_sdr_mode", "secondary_sdr_priority", "secondary_sdr_running",
                         "sdr_pins", "sdr_devices", "op25_sdr_serial", "radio_channels",
-                        "disk_free_bytes", "disk_total_bytes"):
+                        "disk_free_bytes", "disk_total_bytes", "version"):
                 if key in payload:
                     updates[key] = payload[key]
             if "sdr_count" in payload: