fix(ble): simplify reconnection — rely on container restart for clean state

In-container BLE reconnection is unreliable because bleak leaves stale
GATT notification handles after abnormal disconnect, and adapter power-
cycling from within Docker corrupts bleak's internal BlueZ manager state.

New approach:
- On BLE disconnect or keepalive failure, immediately mark as permanently
  failed (no in-container reconnect attempts)
- Health endpoint returns 503, Docker healthcheck triggers container restart
- Docker entrypoint script disconnects stale BLE connections before app
  starts, ensuring clean GATT state for bleak

This is reliable because:
- MeshCore.create_ble(address=...) works on fresh container starts
- The BlueZ daemon on the host maintains adapter state correctly
- Container restart is fast (~5s) and gives a truly clean BLE state

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/docker-entrypoint.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# Docker entrypoint for mc-webui
+#
+# Disconnects stale BLE connections before starting the app.
+# BlueZ on the host auto-reconnects trusted devices, leaving stale GATT
+# notification handles that block bleak from establishing a new session.
+# A clean disconnect here ensures the app starts with a fresh BLE state.
+
+set -e
+
+# If MC_BLE_ADDRESS is set, clean up stale BLE connections
+if [ -n "$MC_BLE_ADDRESS" ]; then
+    DBUS_PATH="/org/bluez/hci0/dev_${MC_BLE_ADDRESS//:/_}"
+
+    # Check if device is connected via BlueZ
+    CONNECTED=$(dbus-send --system --print-reply --dest=org.bluez \
+        "$DBUS_PATH" org.freedesktop.DBus.Properties.Get \
+        string:org.bluez.Device1 string:Connected 2>/dev/null \
+        | grep -c "boolean true" || true)
+
+    if [ "$CONNECTED" = "1" ]; then
+        echo "[entrypoint] BLE device $MC_BLE_ADDRESS is connected, disconnecting stale session..."
+        dbus-send --system --print-reply --dest=org.bluez \
+            "$DBUS_PATH" org.bluez.Device1.Disconnect 2>/dev/null || true
+        sleep 2
+        echo "[entrypoint] Stale BLE connection cleared"
+    fi
+fi
+
+# Run the main application
+exec "$@"