feat: add multi-device provisioning and local remote-config UI

- add multi-device portal device management, key rotation, and sync request APIs
- add Pi settings UI for remote server URL, device name, and API key
- add local test-connection and sync-now actions
- make upload and config sync reuse dynamic shared credentials
- add Phase 25.5c migration and docs updates

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

app.py

@@ -1,5 +1,5 @@
 from flask import Flask, render_template, make_response, json, jsonify, request, send_file, Response
-from modules import app_gps, app_events, app_car, app_account, app_obd, app_sql, app_dash, app_upload, app_video, app_health, app_alerts, app_settings, app_network, app_device_config, app_device_sync
+from modules import app_gps, app_events, app_car, app_account, app_obd, app_sql, app_dash, app_upload, app_video, app_health, app_alerts, app_settings, app_network, app_device_config, app_device_sync, app_remote_config
 import os, time
 from gevent.pywsgi import WSGIServer
 
@@ -64,6 +64,37 @@ def api_device_config():
     _reload_runtime_device_config()
     return jsonify(app_device_config.get_device_config())
 
+@app.route('/api/remote-config', methods=['GET', 'POST'])
+def api_remote_config():
+    if request.method == 'GET':
+        return jsonify(app_remote_config.get_remote_config())
+    errors = {}
+    app_remote_config.update_remote_config(request.get_json(silent=True), errors)
+    if errors:
+        return jsonify(error="Invalid remote config.", fields=errors), 400
+    app_upload.start_uploading()
+    app_device_sync.start_sync()
+    return jsonify(app_remote_config.get_remote_config())
+
+@app.route('/api/remote-config/test', methods=['POST'])
+def api_remote_config_test():
+    result = app_remote_config.test_connection()
+    return jsonify(result), 200 if result.get("ok") else 400
+
+@app.route('/api/remote-config/sync-now', methods=['POST'])
+def api_remote_config_sync_now():
+    try:
+        result = app_device_sync.sync_now()
+    except Exception as error:
+        return jsonify(status="error", message=str(error)), 502
+    status_codes = {
+        "synced": 200,
+        "no_change": 200,
+        "not_configured": 400,
+        "offline": 503,
+    }
+    return jsonify(result), status_codes.get(result["status"], 500)
+
 @app.route('/api/uplink/status')
 def uplink_status():
     try: