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/pr-formatting-check.yml

@@ -0,0 +1,40 @@
+name: "PR Formatting"
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - edited
+      - synchronize
+
+jobs:
+  title-check:
+    name: Title Check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check PR Title Format
+        run: |
+          PR_TITLE="${{ github.event.pull_request.title }}"
+          echo "Checking PR title: $PR_TITLE"
+          
+          # Conventional commit pattern: type(scope): description or type: description
+          # Types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert
+          PATTERN="^(feat|fix|docs|style|refactor|perf|test|build|ci|chore|revert)(\([a-zA-Z0-9_-]+\))?: .+"
+          
+          if echo "$PR_TITLE" | grep -qE "$PATTERN"; then
+            echo "✓ PR title follows conventional commit format"
+          else
+            echo "✗ PR title does not follow conventional commit format"
+            echo ""
+            echo "Expected format: type(scope): description"
+            echo "  or: type: description"
+            echo ""
+            echo "Valid types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert"
+            echo ""
+            echo "Examples:"
+            echo "  feat(reader): add bookmark sync feature"
+            echo "  fix: resolve memory leak in epub parser"
+            echo "  docs: update README with new instructions"
+            exit 1
+          fi