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/models/user_card_import.py

@@ -0,0 +1,33 @@
+"""
+SQLAlchemy ORM model for user card imports.
+
+Stores a user's imported card collection as a JSON string containing
+a list of card names. This is the source data for building decks
+from the user's actual card collection.
+"""
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Text, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from app.core.database import Base
+
+
+class UserCardImport(Base):
+    """
+    User's imported card collection.
+    
+    Stores a JSON string of card names that the user owns.
+    Used as the source for building decks from user's actual cards.
+    """
+    __tablename__ = "user_card_imports"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    user_id = Column(Integer, ForeignKey("mtgonline_users.id", ondelete="CASCADE"), nullable=False, unique=True, index=True)
+    card_names_json = Column(Text, nullable=False)  # JSON array of card names
+    created_at = Column(DateTime, server_default=func.now())
+    updated_at = Column(DateTime, server_default=func.now(), onupdate=func.now())
+
+    # Relationships
+    user = relationship("User", backref="card_imports")
+
+    def __repr__(self) -> str:
+        return f"<UserCardImport user={self.user_id}>"