gitea: fix healthcheck — probe /api/healthz (was 404 on /api/v1/version pre-install)

Surfaced during the unattended deploy sweep: a fresh gitea reported unhealthy because
the HC hit /api/v1/version (404 until install-lock); /api/healthz returns 200 while
serving. Fixed both the docker HC and the controller .felhom.yml probe; bumped
start_period to 90s for first-boot DB migration. Same class as the komga fix.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

templates/gitea/.felhom.yml

@@ -57,7 +57,7 @@ healthcheck:
   checks:
     - type: api
       port: 3000
-      path: "/api/v1/version"
+      # /api/healthz is always available (200) once serving; /api/v1/version 404s pre-install-lock.
+      path: "/api/healthz"
       expect:
         status: 200
-        body_contains: "version"