feat: complete core asset management system with database integration

- Add enhanced AssetManager with database integration and usage tracking
- Implement Asset model with from_dict/to_dict conversion methods
- Add resolve_asset_references() for linking discovered assets to imports
- Integrate AssetDatabase with enhanced schema and performance indexes
- Fix database schema constraints and test compatibility issues
- Add list_assets_as_objects() method for dict-to-object migration
- Resolve 91% of asset management tests (51/56 passing)

Key features:
* Content-addressable asset storage with deduplication
* Database-backed usage statistics and processing logs
* Asset reference resolution from markdown files
* Enhanced performance with indexing and caching
* Object-oriented Asset model with backwards compatibility

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

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

markitect/assets/models.py

@@ -0,0 +1,166 @@
+"""
+Asset model classes for a clean object-oriented interface.
+
+This module provides dataclasses for representing assets with proper
+type hints and methods, following the interface expectations from tests.
+"""
+
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Optional, Dict, Any, List
+from datetime import datetime
+from enum import Enum
+
+
+class ReferenceType(Enum):
+    """Types of asset references in markdown."""
+    IMAGE = "image"
+    LINK = "link"
+    EMBED = "embed"
+    REFERENCE_STYLE = "reference_style"
+
+
+@dataclass
+class Asset:
+    """Represents a managed asset with content-addressable storage."""
+
+    # Core identification
+    content_hash: str
+    filename: str
+
+    # File properties
+    size_bytes: int
+    mime_type: str
+
+    # Storage paths
+    path: str  # Content-addressable storage path
+    original_path: Optional[str] = None
+
+    # Metadata
+    created_at: Optional[datetime] = None
+    description: Optional[str] = None
+    tags: list[str] = field(default_factory=list)
+
+    # Alternative names for compatibility with existing tests
+    @property
+    def size(self) -> int:
+        """Alternative name for size_bytes."""
+        return self.size_bytes
+
+    @property
+    def checksum(self) -> str:
+        """Alternative name for content_hash."""
+        return self.content_hash
+
+    @property
+    def hash(self) -> str:
+        """Alternative name for content_hash."""
+        return self.content_hash
+
+    @property
+    def storage_path(self) -> Path:
+        """Get storage path as Path object."""
+        return Path(self.path)
+
+    def get_extension(self) -> str:
+        """Get file extension."""
+        return Path(self.filename).suffix.lower()
+
+    def is_image(self) -> bool:
+        """Check if asset is an image."""
+        return self.mime_type.startswith('image/')
+
+    def is_document(self) -> bool:
+        """Check if asset is a document."""
+        return self.mime_type in ['application/pdf', 'text/markdown', 'text/plain']
+
+    @classmethod
+    def from_dict(cls, data: Dict[str, Any]) -> 'Asset':
+        """Create Asset from dictionary (for migration from dict-based storage)."""
+        # Handle various field name variations
+        return cls(
+            content_hash=data.get('content_hash', data.get('hash', '')),
+            filename=cls._extract_filename_from_path(data.get('path', '')),
+            size_bytes=data.get('size_bytes', data.get('size', 0)),
+            mime_type=data.get('mime_type', 'application/octet-stream'),
+            path=data.get('path', ''),
+            original_path=data.get('original_path'),
+            created_at=cls._parse_datetime(data.get('created_at')),
+            description=data.get('description'),
+            tags=data.get('tags', [])
+        )
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert Asset to dictionary (for storage)."""
+        return {
+            'content_hash': self.content_hash,
+            'filename': self.filename,
+            'size_bytes': self.size_bytes,
+            'mime_type': self.mime_type,
+            'path': self.path,
+            'original_path': self.original_path,
+            'created_at': self.created_at.isoformat() if self.created_at else None,
+            'description': self.description,
+            'tags': self.tags
+        }
+
+    @staticmethod
+    def _extract_filename_from_path(path: str) -> str:
+        """Extract original filename from storage path when possible."""
+        if not path:
+            return ""
+        storage_path = Path(path)
+        # For content-addressable storage, we'll use the hash + extension
+        return storage_path.name
+
+    @staticmethod
+    def _parse_datetime(dt_str: Optional[str]) -> Optional[datetime]:
+        """Parse datetime string."""
+        if not dt_str:
+            return None
+        try:
+            return datetime.fromisoformat(dt_str.replace('Z', '+00:00'))
+        except (ValueError, AttributeError):
+            return None
+
+
+@dataclass
+class AssetReference:
+    """Represents a reference to an asset from a markdown file."""
+
+    source_file: Path
+    asset_path: str
+    reference_type: str  # 'image', 'link', etc.
+    line_number: int
+    alt_text: str = ""
+    title: str = ""
+    is_broken: bool = False
+    resolved_asset: Optional[Asset] = None
+
+
+@dataclass
+class AssetCollection:
+    """Represents a collection of assets with metadata."""
+
+    assets: list[Asset] = field(default_factory=list)
+    total_size: int = 0
+    created_at: Optional[datetime] = None
+
+    def __post_init__(self):
+        """Calculate total size."""
+        self.total_size = sum(asset.size_bytes for asset in self.assets)
+
+    def filter_by_type(self, mime_type_prefix: str) -> 'AssetCollection':
+        """Filter assets by MIME type prefix."""
+        filtered = [asset for asset in self.assets
+                   if asset.mime_type.startswith(mime_type_prefix)]
+        return AssetCollection(assets=filtered)
+
+    def get_images(self) -> 'AssetCollection':
+        """Get only image assets."""
+        return self.filter_by_type('image/')
+
+    def get_documents(self) -> 'AssetCollection':
+        """Get only document assets."""
+        docs = [asset for asset in self.assets if asset.is_document()]
+        return AssetCollection(assets=docs)