Fix Gitea Actions registry auth: use a PAT instead of the auto token

The automatic GITHUB_TOKEN doesn't reliably authenticate against Gitea's
Container Registry -- confirmed as a known, still-open limitation across
several Gitea versions (multiple upstream issues, consistent with the
401/unauthorized error hit here). Gitea's own community guidance is to
use a real Personal Access Token instead. Switches docker/login-action to
a REGISTRY_TOKEN repo secret (a PAT with package write scope, created in
Gitea's user settings) with an explicit username rather than the
gitea.actor context, and drops the now-unused permissions: packages:
write block that only applied to the auto token.

.gitea/workflows/server-docker-build.yml

@@ -10,9 +10,6 @@ on:
 jobs:
   build-and-push:
     runs-on: ubuntu-latest
-    permissions:
-      contents: read
-      packages: write
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -24,8 +21,8 @@ jobs:
         uses: docker/login-action@v3
         with:
           registry: git.thumeit.com
-          username: ${{ gitea.actor }}
+          username: tfaour
-          password: ${{ secrets.GITHUB_TOKEN }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
 
       - name: Build and push
         uses: docker/build-push-action@v6