feat(ci): build custom Docker images for Gitea Actions compatibility

- Create Dockerfile.ci-base with Bun, Node.js, and Playwright pre-installed
- Add build-ci-images workflow that triggers on package.json changes
- Update PR workflow to use custom ci-base image instead of GitHub Actions
- Update Release workflow to use custom ci-base image
- Remove dependency on oven/setup-bun@v2 GitHub Action
- Remove dependency on docker/setup-buildx-action GitHub Action
- Images are automatically built when dependencies in package.json update
- Weekly scheduled rebuild ensures tools stay current

This resolves the 'authentication required: Repository not found' error
when Gitea Actions tries to clone GitHub Actions from external repositories.

.gitea/workflows/pr.yml

@@ -9,7 +9,7 @@ jobs:
   unit-tests:
     runs-on: ubuntu-latest
     container:
-      image: oven/bun:alpine
+      image: docker.notsosm.art/euchre-camp/ci-base:latest
       options: --user root
 
     steps:
@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: unit-tests
     container:
-      image: mcr.microsoft.com/playwright:v1.58.0-jammy
+      image: docker.notsosm.art/euchre-camp/ci-base:latest
       options: --user root
     env:
       DATABASE_PROVIDER: sqlite
@@ -42,11 +42,6 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Setup Bun
-        uses: oven/setup-bun@v2
-        with:
-          bun-version: latest
-
       - name: Install dependencies
         run: bun install