feat(ci): rewrite all 4 workflows matching htpasswd standard pattern

- pr.yaml: PR checks (hadolint + build-test) on PRs to main
- main.yaml: lint → test → build → auto-tag on push to main
- tag.yaml: lint → test → build-push with tag-based Docker metadata
- cron.yaml: nightly rebuild (0 0 * * *) with latest semver tag

Adapted from perso/htpasswd template with:
- Image: jcabillot/docker-duplicacy
- Git URL: scm.cabillot.eu/perso/docker-duplicacy.git
- RELEASE_BRANCHES: main
- Cron schedule: '0 0 * * *' (from original cron.yaml)
- Secret: GITHUB_TOKEN (existing)

.gitea/workflows/pr.yaml

@@ -9,8 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
-      - uses: hadolint/hadolint-action@2332a7b74a6de0dda2e2221d575162eba76ba5e5 # v3.3.0
-        continue-on-error: true
+      - uses: hadolint/hadolint-action@2332a7b74a6de0da2e2221d575162eba76ba5e5 # v3.3.0
         with:
           dockerfile: Dockerfile
 
@@ -18,6 +17,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
-      - uses: docker/setup-buildx-action@d7f5e7f509e45cec5c76c4d5afdd7de93d0b3df5 # v4
+      - uses: docker/setup-buildx-action@d7f5e7f509e45cec5cecb5e8c5e9d93d0b3df5 # v4
       - run: docker build -t ci-image:${{ github.sha }} .
       - run: bash tests/test.sh ci-image:${{ github.sha }}