fix: prioritize GITEA_SERVER_URL over GITHUB_SERVER_URL for custom Gitea instances

- Modified config.ts to check GITEA_SERVER_URL first, then fall back to GITHUB_SERVER_URL
- Fixes issue where container-based Gitea instances generate internal URLs in comments
- Added comprehensive test suite for URL configuration scenarios
- Updated README.md with configuration documentation and examples
- Added example workflow file for custom URL setup
- Fixed TypeScript configuration to support Node.js globals

Resolves issue #4: Enable GITEA_SERVER_URL environment variable override

examples/gitea-custom-url.yml

@@ -0,0 +1,23 @@
+name: Claude PR Review with Custom Gitea URL
+on:
+  pull_request:
+    types: [opened, synchronize]
+  issue_comment:
+    types: [created]
+
+jobs:
+  claude-review:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Claude Code Analysis
+        uses: markwylde/claude-code-gitea-action@gitea
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          claude-api-key: ${{ secrets.CLAUDE_API_KEY }}
+        env:
+          # Set this to your public Gitea URL to override the internal container URL
+          # This ensures that links in comments point to the correct public URL
+          GITEA_SERVER_URL: https://gitea.example.com
+          
+          # Note: GITHUB_SERVER_URL is automatically set by Gitea Actions to the internal URL
+          # but it will be overridden by GITEA_SERVER_URL if set above