Use a full fetch in CI: Gitea fails to pack a shallow clone

actions/checkout defaults to depth=1, and Gitea aborted generating that pack
with a bad pack header protocol error on all three retries, failing the build
before any image was pushed. A full fetch avoids the shallow-pack path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -14,7 +14,13 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      # fetch-depth: 0 on purpose. The default depth=1 shallow fetch made Gitea
+      # die generating the pack ("fatal: protocol error: bad pack header",
+      # retried three times and failed the run). A full fetch takes the slow
+      # path on the server and works. Don't "optimise" this back to depth=1.
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3