collector: survive bluetoothd hangs and restarts

- every BlueZ call runs off the asyncio thread with a timeout; if bluetoothd
  stays unresponsive for 30 s the collector restarts bluetooth.service and
  exits for a clean re-registration
- Type=notify + WatchdogSec for buttontask-collector, never give up restarting
- bluetooth.service drop-in: Restart=always (BlueZ 5.55 crashes on assert/SEGV),
  installed by device-install.sh and OTA (bt-update)
- bt-service: bluez-restart action for the collector

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

webconfig/bluetooth.service.d/override.conf

@@ -0,0 +1,10 @@
+# Installed as /etc/systemd/system/bluetooth.service.d/override.conf
+# bluetoothd 5.55 on this board crashes now and then (GLib assert / SEGV).
+# Stock unit has no Restart=, so after a crash BLE stayed dead until something
+# happened to D-Bus-activate it again.
+[Unit]
+StartLimitIntervalSec=0
+
+[Service]
+Restart=always
+RestartSec=2

webconfig/buttontask-collector.service

@@ -2,9 +2,17 @@
 Description=ButtonTask BLE Sensor Collector
 After=bluetooth.service dbus.service
 Wants=bluetooth.service
+# Never give up restarting: the collector exits on purpose whenever
+# bluetoothd restarts or hangs, to re-register GATT/advertising from scratch.
+StartLimitIntervalSec=0
 
 [Service]
-Type=simple
+# Type=notify + watchdog: the collector sends READY=1 after GATT start and
+# WATCHDOG=1 every loop tick; a stuck event loop gets killed and restarted.
+Type=notify
+NotifyAccess=main
+WatchdogSec=60
+TimeoutStartSec=90
 User=buttontask
 Group=buttontask
 SupplementaryGroups=bluetooth
@@ -12,7 +20,7 @@ WorkingDirectory=/opt/buttontask/current/collector
 Environment=BUTTONTASK_ROOT=/opt/buttontask
 Environment=PYTHONUNBUFFERED=1
 ExecStart=/usr/bin/python3 /opt/buttontask/current/collector/main.py
-Restart=on-failure
+Restart=always
 RestartSec=3
 
 [Install]

webconfig/scripts/bt-service

@@ -48,6 +48,10 @@ run_action() {
         collector-off)
             systemctl disable --now buttontask-collector
             ;;
+        bluez-restart)
+            # Called by the collector when bluetoothd stops answering D-Bus.
+            systemctl restart bluetooth
+            ;;
         units)
             systemctl list-units --type=service --all --no-legend --plain --no-pager \
                 || systemctl list-units --type=service --all --no-legend --no-pager
@@ -60,7 +64,7 @@ run_action() {
             emit_journal
             ;;
         *)
-            echo "usage: bt-service {start|stop|restart|collector-on|collector-off|units|journal}" >&2
+            echo "usage: bt-service {start|stop|restart|collector-on|collector-off|bluez-restart|units|journal}" >&2
             exit 2
             ;;
     esac

webconfig/scripts/bt-update

@@ -210,6 +210,13 @@ cmd_stage() {
         fi
         log "synced buttontask-collector.service"
     fi
+    if [ -f "$dest/webconfig/bluetooth.service.d/override.conf" ]; then
+        install -d /etc/systemd/system/bluetooth.service.d
+        sed 's/\r$//' "$dest/webconfig/bluetooth.service.d/override.conf" \
+            > /etc/systemd/system/bluetooth.service.d/override.conf
+        systemctl daemon-reload 2>/dev/null || true
+        log "synced bluetooth.service.d/override.conf"
+    fi
 
     write_status switching "$ver"
     switch_to "$dest"