fix(ci): use system Python instead of setup-python action

The setup-python action has hardcoded paths that fail on self-hosted
macOS runners. Use system Python directly instead.

Also simplified clang-format step to use system version if available.

.gitea/workflows/release.yml

@@ -4,9 +4,6 @@ on:
     tags:
       - '*'
 
-env:
-  RUNNER_TOOL_CACHE: ${{ runner.temp }}/tool_cache
-
 jobs:
   build-release:
     runs-on: ubuntu-latest
@@ -15,22 +12,14 @@ jobs:
         with:
           submodules: recursive
 
-      - uses: actions/cache@v4
-        with:
-          path: |
-            ~/.cache/pip
-            ~/.platformio/.cache
-          key: ${{ runner.os }}-pio
-
-      - name: Set up Python tool cache directory
-        run: mkdir -p "$RUNNER_TOOL_CACHE"
-
-      - uses: actions/setup-python@v5
-        with:
-          python-version: '3.12'
+      - name: Set up Python
+        run: |
+          # Use system Python on self-hosted runner
+          python3 --version
+          python3 -m pip install --upgrade pip
 
       - name: Install PlatformIO Core
-        run: pip install --upgrade platformio
+        run: python3 -m pip install --upgrade platformio
 
       - name: Build CrossPoint
         run: pio run -e gh_release