fix: remove Docker Hub registry cache to unblock builds

Registry cache export consistently fails with 400 Bad Request from
Docker Hub, likely due to blob size limits on the free tier after the
base image change. Removing cache-from/cache-to entirely — builds are
fast enough without it (~2 min), and we can re-add with a local cache
backend later if needed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -55,8 +55,6 @@ jobs:
           context: .
           push: true
           tags: ${{ steps.tags.outputs.tags }}
-          cache-from: type=registry,ref=manticorum67/paper-dynasty-database:buildcache
-          cache-to: type=registry,ref=manticorum67/paper-dynasty-database:buildcache,mode=min
 
       - name: Tag release
         if: success() && github.ref == 'refs/heads/main'