Add Dockerfile, fix SQLite immutable mode, URL-encode credentials

- Dockerfile: multi-stage build with golang:1.26 and alpine + ffmpeg
- SQLite: use file: URI with immutable=1 for read-only access
- URL builder: encode user/pass with PathEscape/QueryEscape for
  special characters (@, \, :, etc.)
- Health endpoint: truncate uptime to seconds
- Release skill: update smoke test to /api endpoint
- Remove unused ValidateID function

internal/probe/probe.go

@@ -29,7 +29,7 @@ func Init() {
 	log = app.GetLogger("probe")
 
 	var err error
-	db, err = sql.Open("sqlite3", app.DB+"?mode=ro")
+	db, err = sql.Open("sqlite3", "file:"+app.DB+"?mode=ro&immutable=1")
 	if err != nil {
 		log.Error().Err(err).Msg("[probe] db open")
 	}