feat: persistent container log collection, unified rotation, logs page redesign

- log_manager: add collect_container_logs (appends docker logs to container_<name>.log),
  get_container_log_lines, rotate_container_log, get_all_log_file_infos
- app.py: new endpoints /api/logs/files (all log file sizes), /api/logs/containers/<name>
  (collect+return stored container logs); rotate endpoint now handles both service and container logs
- Logs page: split into API Service Logs tab (python manager logs) and Container Logs tab
  (persistent docker stdout/stderr); Statistics tab shows both kinds with per-row rotate;
  each tab has a description explaining what it shows and where files live
- wireguard_manager: test_connectivity peer_ip=None guard (already in previous commit, now rebuilt)

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

api/app.py

@@ -619,17 +619,43 @@ def get_log_statistics():
 
 @app.route('/api/logs/rotate', methods=['POST'])
 def rotate_logs():
-    """Manually rotate logs."""
+    """Manually rotate logs (API service log or container log)."""
     try:
         data = request.get_json(silent=True) or {}
-        service = data.get('service')
-        
-        log_manager.rotate_logs(service)
+        name = data.get('name')   # e.g. 'wireguard' or 'container_cell-api'
+        kind = data.get('kind', 'service')  # 'service' or 'container'
+
+        if kind == 'container':
+            container_name = name[len('container_'):] if name and name.startswith('container_') else name
+            log_manager.rotate_container_log(container_name)
+        else:
+            log_manager.rotate_logs(name)
         return jsonify({"message": "Logs rotated successfully"})
     except Exception as e:
         logger.error(f"Error rotating logs: {e}")
         return jsonify({"error": str(e)}), 500
 
+@app.route('/api/logs/files', methods=['GET'])
+def get_log_file_infos():
+    """List all stored log files (service + container) with sizes."""
+    try:
+        return jsonify(log_manager.get_all_log_file_infos())
+    except Exception as e:
+        logger.error(f"Error listing log files: {e}")
+        return jsonify({"error": str(e)}), 500
+
+@app.route('/api/logs/containers/<container_name>', methods=['GET'])
+def get_stored_container_logs(container_name):
+    """Collect latest docker logs into file and return last N lines."""
+    try:
+        tail = int(request.args.get('tail', 100))
+        log_manager.collect_container_logs(container_name)
+        lines = log_manager.get_container_log_lines(container_name, tail)
+        return jsonify({'container': container_name, 'lines': lines})
+    except Exception as e:
+        logger.error(f"Error getting stored container logs for {container_name}: {e}")
+        return jsonify({"error": str(e)}), 500
+
 # Network Services API
 @app.route('/api/dns/records', methods=['GET'])
 def get_dns_records():