fix: wire Phase 25.5a deploy docs and sync connectivity

- use app_network status for device sync connectivity checks
- mount migrate_phase25_5a.sql in server docker compose
- document manual server upgrade migration steps
- record verified Pi and unraid SSH access details in PLAN

Co-authored-by: Copilot <[email protected]>

modules/app_device_sync.py

@@ -4,11 +4,14 @@ Pi fetches device config from server when internet is available (connection-driv
 Stores in SQLite and hot-reloads app globals if config changes.
 """
 
+import os
+import subprocess
 import threading
 import time
-import os
+
 import requests
-from . import app_sql
+
+from . import app_network, app_sql
 
 
 _SYNC_THREAD = None
@@ -16,6 +19,20 @@ _SYNC_STOP = False
 _SYNC_CONFIG_VERSION = 0  # Track last-synced version to detect changes
 
 
+def _has_internet():
+    """Use the existing NetworkManager-derived status instead of probing 8.8.8.8 over HTTP."""
+    try:
+        return app_network.get_status().get("internet_reachable", False)
+    except (
+        OSError,
+        subprocess.SubprocessError,
+        ValueError,
+        KeyError,
+        app_network.NetworkConfigurationError,
+    ):
+        return False
+
+
 def start_sync():
     """Start background device config sync thread."""
     global _SYNC_THREAD, _SYNC_STOP
@@ -49,12 +66,7 @@ def _sync_loop():
     
     while not _SYNC_STOP:
         try:
-            # Check if internet is available (simple connectivity test)
-            try:
-                requests.head("http://8.8.8.8", timeout=2)
-                is_connected = True
-            except (requests.RequestException, Exception):
-                is_connected = False
+            is_connected = _has_internet()
             
             if is_connected:
                 # Fetch device config from server