feat: implement universal issue tracking facade

Add comprehensive issue tracking facade system that provides a unified CLI interface to any issue tracking backend. The facade automatically detects the repository's issue tracker and provides consistent commands across all platforms.

Key features:
- Repository-aware automatic backend detection (GitHub, GitLab, Gitea, local SQLite)
- Unified CLI interface with same commands across all backends
- Plugin architecture for extensible backend support
- Local SQLite backend for offline development
- Gitea backend with full API integration
- Bidirectional synchronization between backends
- Performance-optimized domain models with caching
- Clean architecture with separation of concerns

The facade acts as a "universal remote control" for issue tracking systems, eliminating the need to learn different CLIs for each platform while providing seamless offline capability and cross-platform consistency.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

issue-facade/cli/__init__.py

@@ -0,0 +1,20 @@
+"""
+Command Line Interface for Universal Issue Tracking
+
+Provides a comprehensive CLI for managing issues across different backends.
+The CLI is designed to be intuitive and follows common patterns from
+tools like git, gh (GitHub CLI), and similar utilities.
+
+Commands:
+- issue list: List issues
+- issue show: Show issue details
+- issue create: Create new issue
+- issue edit: Edit existing issue
+- issue close: Close issue
+- issue reopen: Reopen issue
+- issue comment: Add comment
+- issue label: Manage labels
+- issue assign: Manage assignments
+- backend: Manage backends
+- sync: Synchronization operations
+"""