ci: add Gitea Actions workflows

Adapt GitHub Actions workflows for self-hosted Gitea instance:
- CI workflow with PlatformIO build, cppcheck, and clang-format
- PR title format checker using conventional commits
- Release workflow for tagged builds

Keeps original .github/workflows/ for upstream compatibility.

.gitea/workflows/ci.yml

@@ -0,0 +1,37 @@
+name: CI
+'on':
+  push:
+    branches: [master, crosspoint-ef]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - name: Install PlatformIO Core
+        run: pip install --upgrade platformio
+
+      - name: Install clang-format-21
+        run: |
+          wget https://apt.llvm.org/llvm.sh
+          chmod +x llvm.sh
+          sudo ./llvm.sh 21
+          sudo apt-get update
+          sudo apt-get install -y clang-format-21
+
+      - name: Run cppcheck
+        run: pio check --fail-on-defect low --fail-on-defect medium --fail-on-defect high
+
+      - name: Run clang-format
+        run: PATH="/usr/lib/llvm-21/bin:$PATH" ./bin/clang-format-fix && git diff --exit-code || (echo "Please run 'bin/clang-format-fix' to fix formatting issues" && exit 1)
+
+      - name: Build CrossPoint
+        run: pio run