feat: add card import feature with fuzzy matching

- Add UserCardImport model (stores imported card names as JSON)
- Create card_import_schemas.py with request/response models
- Create card_import.py router with import/get/delete endpoints
- Add Alembic migration 004 (user_card_imports table)
- Fuzzy matching for card name matching (60% threshold)
- Integration with deckbuilding via imported cards
- Endpoints: GET /api/v1/card-import/status, POST /, DELETE /, GET /summary

backend/app/schemas/card_import_schemas.py

@@ -0,0 +1,70 @@
+"""
+Pydantic schemas for card import feature.
+
+Provides request/response models for importing card collections
+and using them for deckbuilding.
+"""
+from pydantic import BaseModel, Field
+from typing import List, Optional, Dict, Any
+from datetime import datetime
+
+
+class CardImportRequest(BaseModel):
+    """Request body for importing card collection."""
+    card_names: List[str] = Field(
+        ...,
+        min_length=1,
+        max_length=10000,
+        description="List of card names to import",
+        examples=[["Lightning Bolt", "Shock", "Thoughtseize"]]
+    )
+
+
+class CardImportResponse(BaseModel):
+    """Response after successful card import."""
+    message: str
+    card_count: int
+    card_names: List[str]
+    imported_at: datetime
+
+
+class CardImportStatusResponse(BaseModel):
+    """Response showing current import status."""
+    has_import: bool
+    card_count: Optional[int] = None
+    card_names: Optional[List[str]] = None
+    last_imported: Optional[datetime] = None
+
+
+class CardMatchResult(BaseModel):
+    """Result of matching imported card name to database card."""
+    card_id: Optional[int] = None
+    card_name: str
+    matched_name: str
+    match_type: str  # 'exact', 'fuzzy', 'partial'
+    confidence: float  # 0.0 to 1.0
+
+
+class CardImportSummary(BaseModel):
+    """Summary of card import with match results."""
+    total_cards: int
+    matched_cards: List[CardMatchResult]
+    unmatched_cards: List[str]
+    import_id: Optional[int] = None
+
+
+# Generic response models
+class MessageResponse(BaseModel):
+    """Generic message response."""
+    message: str
+
+
+class CountResponse(BaseModel):
+    """Generic count response."""
+    count: int
+
+
+class ErrorResponse(BaseModel):
+    """Error response with details."""
+    detail: str
+    error_code: Optional[str] = None