Standardize workflows to htpasswd pattern

Transform all 4 workflow files to match the standard pattern used by
perso/htpasswd (and offlineimap):

main.yaml:
  - Rename to 'Main Release'
  - hadolint (continue-on-error, dockerfile param) → test (build ci-image, run tests)
  → build (no push, just build target image) → tag (fetch-depth 0, git auth with
    SA_TOKEN_ACTION_PUSH_TAGS, semver tagging)

cron.yaml:
  - Keep original schedule '0 0 * * *'
  - hadolint → test → build-push (get-latest-tag, metadata with -latest
    only, no :latest tag)

tag.yaml:
  - hadolint → test → build-push (type=ref,event=tag + suffix=-latest)

pr.yaml:
  - hadolint (no continue-on-error, add dockerfile param) → build-test
  - Scope to pull_request branches: [master]
  - Use ci-image pattern with buildx setup

.gitea/workflows/pr.yaml

@@ -2,24 +2,21 @@ name: PR Checks
 
 on:
   pull_request:
+    branches: [master]
 
 jobs:
   hadolint:
     runs-on: ubuntu-latest
     steps:
-      - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
-      - name: Hadolint
-        uses: hadolint/hadolint-action@2332a7b74a6de0dda2e2221d575162eba76ba5e5 # v3.3.0
-        continue-on-error: true
+      - uses: actions/checkout@df4cb1c069e1874edd31b4111f1884172cec0e10 # v6
+      - uses: hadolint/hadolint-action@2332a7b74a6de0dda2e2221d575162eba76ba5e5 # v3.3.0
+        with:
+          dockerfile: Dockerfile
 
   build-test:
     runs-on: ubuntu-latest
-    needs: hadolint
     steps:
-      - name: Checkout
-        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
-      - name: Build image
-        run: docker build -t ci-image:${{ github.sha }} .
-      - name: Run tests
-        run: bash tests/test.sh ci-image:${{ github.sha }}
+      - uses: actions/checkout@df4cb1c069e1874edd31b4111f1884172cec0e10 # v6
+      - uses: docker/setup-buildx-action@d7f5e7f509e9e45cece5cec9e8c9e4f5afdd7de9 # v4
+      - run: docker build -t ci-image:${{ github.sha }} .
+      - run: bash tests/test.sh ci-image:${{ github.sha }}