feat: Implement CLI entry point and basic commands for Issue #12

Complete CLI implementation using Click framework with core commands:
- ingest: Process and store markdown files with progress feedback
- status: Display file processing status and metadata
- list: Show all stored files with optional verbose details

Features:
- Global options (--verbose, --config, --database)
- Comprehensive error handling and user-friendly output
- Integration with existing DatabaseManager and DocumentManager
- Proper console script configuration in pyproject.toml
- Extensive inline documentation and help text
- Robust front matter parsing with error handling

Technical Implementation:
- Added Click dependency (>=8.0.0) to pyproject.toml
- Console script entry point: markitect.cli:main
- Full integration with database and caching systems
- Performance-aware implementation maintaining existing architecture

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

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

pyproject.toml

@@ -8,7 +8,10 @@ version = "0.1.0"
 description = "Advanced Markdown engine for structured content"
 readme = "README.md"
 requires-python = ">=3.8"
-dependencies = ["markdown-it-py", "PyYAML"]
+dependencies = ["markdown-it-py", "PyYAML", "click>=8.0.0"]
+
+[project.scripts]
+markitect = "markitect.cli:main"
 
 [tool.setuptools.packages.find]
 include = ["markitect*"]