feat(action): add composite action for changelog and release

- Introduces a composite GitHub Action to automate changelog generation
  and Gitea release processes
- Includes version detection, changelog updates, and release steps
- Supports configurable author details and optional PAT for API access

action.yml

@@ -0,0 +1,55 @@
+name: Auto Changelog & Release
+description: "One-stop composite action for version-bump detection, changelog generation and Gitea release."
+
+inputs:
+  token:
+    description: "Gitea/GitHub PAT für Release-API"
+    required: false
+  author_name:
+    description: "Commit-Autorname"
+    required: false
+  author_email:
+    description: "Commit-Autore-Mail"
+    required: false
+runs:
+  using: "composite"
+  steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+
+    - name: Detect version change
+      shell: bash
+      id: detect
+      run: |
+        bash ${{ github.action_path }}/scripts/detect-version-change.sh
+
+    - name: Read CLIFF_VERSION
+      shell: bash
+      id: cliff_version
+      run: bash ${{ github.action_path }}/scripts/read-cliff-version.sh
+
+    - name: Install git-cliff
+      shell: bash
+      run: |
+        bash ${{ github.action_path }}/scripts/install-git-cliff.sh "${{ steps.cliff_version.outputs.version }}"
+
+    - name: Set up git
+      shell: bash
+      run: |
+        bash ${{ github.action_path }}/scripts/setup-git.sh \
+          "${{ inputs.author_name }}" \
+          "${{ inputs.author_email }}"
+
+    - name: Generate and commit changelog (unreleased)
+      if: steps.detect.outputs.version_changed == 'false' || github.ref != 'refs/heads/main'
+      shell: bash
+      run: bash ${{ github.action_path }}/scripts/generate-unreleased-changelog.sh
+
+    - name: Release from VERSION
+      if: steps.detect.outputs.version_changed == 'true' && github.ref == 'refs/heads/main'
+      shell: bash
+      env:
+        RELEASE_PUBLISH_TOKEN: ${{ inputs.token }}
+      run: bash ${{ github.action_path }}/scripts/release-from-version.sh