fix(home-assistant): healthcheck uses /manifest.json instead of authenticated /api/

The /api/ endpoint requires authentication, causing healthcheck to always
fail and spam HA logs with "invalid authentication" warnings.

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

templates/home-assistant/docker-compose.yml

@@ -22,7 +22,7 @@ services:
         limits:
           memory: 1024M
     healthcheck:
-      test: ["CMD", "curl", "-f", "http://localhost:8123/api/"]
+      test: ["CMD", "curl", "-sf", "http://localhost:8123/manifest.json"]
       interval: 30s
       timeout: 5s
       retries: 3