fix(gitea): revert to UMAMI_ID/UMAMI_SRC and use .UmamiSrc/.UmamiId template vars

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

gitea/compose.yml

@@ -37,7 +37,7 @@ services:
       GITEA__ui__DEFAULT_THEME: nord
       GITEA__ui__ENABLE_FEED: "true"
       UMAMI_SRC: ${UMAMI_SRC}
-      UMAMI_SCRIPT: ${UMAMI_SCRIPT}
+      UMAMI_ID: ${UMAMI_ID}
     ports:
       - "2222:2222"
     volumes: