Tag plugin logs structurally and surface the active plugin in System Logs

- get_logger() now returns a PluginLoggerAdapter when given a plugin_id,
  so every plugin log call is stamped with plugin_id automatically instead
  of only calls that explicitly passed extra={'plugin_id': ...}. This makes
  the "[Plugin: x]" prefix reliable in the journalctl-backed log stream.
- display_controller publishes the currently active mode/plugin to the
  shared cache whenever it changes, exposed via a new
  GET /api/v3/display/current-status endpoint.
- System Logs page: adds a "Now showing" banner backed by that endpoint, a
  plugin filter dropdown (populated from parsed log lines), a plugin badge
  per log entry, and fixes log parsing to handle the short-iso timestamp
  format journalctl actually returns (the old regex only matched syslog
  timestamps, so level/plugin extraction silently never ran).

web_interface/blueprints/api_v3.py

@@ -6891,6 +6891,29 @@ def list_plugin_assets():
         logger.error('Unhandled exception', exc_info=True)
         return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details'}), 500
 
+@api_v3.route('/display/current-status', methods=['GET'])
+def get_current_display_status():
+    """Return the display mode/plugin currently intended to be shown.
+
+    Published by the display process (display_controller._publish_current_mode_state)
+    to the shared cache whenever the active mode changes, so the web UI (e.g. the
+    System Logs page) can show what's on screen without querying the display
+    process directly.
+    """
+    try:
+        cache = _ensure_cache_manager()
+        state = cache.get('display_current_state', max_age=120)
+        if state is None:
+            state = {
+                'mode': None,
+                'plugin_id': None,
+                'last_updated': None,
+            }
+        return jsonify({'status': 'success', 'data': state})
+    except Exception:
+        logger.error('Error in get_current_display_status', exc_info=True)
+        return jsonify({'status': 'error', 'message': 'An error occurred; see logs for details'}), 500
+
 @api_v3.route('/logs', methods=['GET'])
 def get_logs():
     """Get system logs from journalctl"""