feat: Implement Issue #1 - Database initialization and front matter parsing

Complete TDD implementation of core MarkiTect functionality:

**Database Module (markitect/database.py):**
- DatabaseManager class with SQLite database initialization
- markdown_files table with proper schema (id, filename, front_matter, content, created_at)
- Front matter storage as JSON with content separation
- File storage, retrieval, and listing methods
- Comprehensive error handling

**Front Matter Module (markitect/frontmatter.py):**
- FrontMatterParser class with YAML front matter parsing
- Clean separation of metadata from markdown content
- Graceful handling of invalid YAML and missing front matter
- Regex-based parsing with proper delimiter handling

**Dependencies:**
- Added PyYAML for front matter parsing
- Updated pyproject.toml with new dependency

**Test Coverage:**
- 9 comprehensive tests covering all functionality
- Database initialization and schema validation
- Front matter parsing with Issue #1 example content
- Integrated workflow testing (storage/retrieval)
- Error handling for edge cases

**TDD Process:**
- RED phase: 8 failing tests defining requirements
- GREEN phase: Minimal implementation making all tests pass
- Validation: Complete workflow verified with example content

This implementation provides the foundation for all subsequent MarkiTect
features, handling the exact example from Issue #1 specification.

Issue #1: Initialize Database and Store Example Markdown File
coulomb/markitect_project#1

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

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

markitect/frontmatter.py

@@ -0,0 +1,60 @@
+"""
+Front matter parsing functionality for MarkiTect.
+
+This module provides YAML front matter parsing for markdown files,
+separating metadata from content.
+"""
+
+import re
+import yaml
+from typing import Dict, Tuple, Any
+
+
+class FrontMatterParser:
+    """Parser for YAML front matter in markdown files."""
+
+    def __init__(self):
+        """Initialize the front matter parser."""
+        pass
+
+    def parse(self, content: str) -> Tuple[Dict[str, Any], str]:
+        """
+        Parse front matter from markdown content.
+
+        Args:
+            content: Raw markdown content that may include YAML front matter
+
+        Returns:
+            Tuple of (front_matter_dict, markdown_content)
+            - front_matter_dict: Parsed YAML as dictionary, empty dict if none
+            - markdown_content: Markdown content with front matter removed
+        """
+        if not content.strip():
+            return {}, content
+
+        # Check if content starts with front matter delimiter
+        if not content.strip().startswith('---'):
+            return {}, content
+
+        # Pattern to match YAML front matter
+        # Must start with --- at beginning of string, end with --- on its own line
+        pattern = r'^---\s*\n(.*?)\n---\s*\n(.*)$'
+        match = re.match(pattern, content, re.DOTALL)
+
+        if not match:
+            # No valid front matter found
+            return {}, content
+
+        yaml_content = match.group(1)
+        markdown_content = match.group(2)
+
+        # Parse YAML content
+        try:
+            front_matter = yaml.safe_load(yaml_content)
+            if front_matter is None:
+                front_matter = {}
+        except yaml.YAMLError:
+            # Invalid YAML - return empty dict and preserve content
+            front_matter = {}
+
+        return front_matter, markdown_content