feat(monitor): store plugin version separately from openclaw version

- Add server_states.plugin_version column
- Keep openclaw_version for remote OpenClaw runtime version
- Expose plugin_version in monitor server view
- Accept and persist plugin_version in heartbeat payloads

app/main.py

@@ -220,6 +220,10 @@ def _migrate_schema():
             db.execute(text("ALTER TABLE monitored_servers ADD COLUMN api_key VARCHAR(64) NULL"))
             db.execute(text("CREATE UNIQUE INDEX idx_monitored_servers_api_key ON monitored_servers (api_key)"))
 
+        # --- server_states.plugin_version for monitor plugin telemetry ---
+        if _has_table(db, "server_states") and not _has_column(db, "server_states", "plugin_version"):
+            db.execute(text("ALTER TABLE server_states ADD COLUMN plugin_version VARCHAR(64) NULL"))
+
         db.commit()
     except Exception as e:
         db.rollback()