Add reusable Forgejo Actions

Composite actions for CI/CD workflows:
- checkout: Clone repo with configurable depth
- docker-build: Build Docker images with multiple tags
- docker-push: Push to Forgejo Packages registry
- create-tag: Auto-increment semantic version tags
- create-issue: Create issues via Forgejo API
- create-pr: Create pull requests via Forgejo API
- comment-pr: Add comments to PRs via Forgejo API

All actions use shell scripts (no Node.js required).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-build/action.yaml

@@ -0,0 +1,62 @@
+name: Docker Build
+description: Build a Docker image with tags
+
+inputs:
+  image:
+    description: Full image name (registry/org/name)
+    required: true
+  tags:
+    description: Comma-separated list of tags
+    default: 'latest'
+  context:
+    description: Build context path
+    default: '.'
+  dockerfile:
+    description: Path to Dockerfile
+    default: 'Dockerfile'
+  build-args:
+    description: Build arguments (KEY=value, newline-separated)
+    default: ''
+
+outputs:
+  images:
+    description: Built image references
+    value: ${{ steps.build.outputs.images }}
+
+runs:
+  using: composite
+  steps:
+    - id: build
+      shell: bash
+      run: |
+        IMAGE="${{ inputs.image }}"
+        TAGS="${{ inputs.tags }}"
+        CONTEXT="${{ inputs.context }}"
+        DOCKERFILE="${{ inputs.dockerfile }}"
+        BUILD_ARGS="${{ inputs.build-args }}"
+
+        # Build tag arguments
+        TAG_ARGS=""
+        IMAGES=""
+        IFS=',' read -ra TAG_ARRAY <<< "$TAGS"
+        for tag in "${TAG_ARRAY[@]}"; do
+          tag=$(echo "$tag" | xargs)  # trim whitespace
+          TAG_ARGS="$TAG_ARGS -t $IMAGE:$tag"
+          IMAGES="$IMAGES$IMAGE:$tag,"
+        done
+        IMAGES="${IMAGES%,}"  # remove trailing comma
+
+        # Build build-arg arguments
+        BUILD_ARG_ARGS=""
+        if [ -n "$BUILD_ARGS" ]; then
+          while IFS= read -r arg; do
+            if [ -n "$arg" ]; then
+              BUILD_ARG_ARGS="$BUILD_ARG_ARGS --build-arg $arg"
+            fi
+          done <<< "$BUILD_ARGS"
+        fi
+
+        # Build the image
+        docker build $TAG_ARGS $BUILD_ARG_ARGS -f "$DOCKERFILE" "$CONTEXT"
+
+        echo "images=$IMAGES" >> $GITHUB_OUTPUT