Phase 3: Schema Layer - Pydantic v2 migration, deduplication, and missing schemas

- Migrated all schemas to Pydantic v2 syntax (model_config, ConfigDict)
- Fixed mutable default in ProtoMessageBase using Field(default_factory=datetime.now)
- Consolidated CardCollection and Wishlist schemas in user_card_collection.py
- Created game_schemas.py with GameCreate, GameResponse, GameJoinRequest, etc.
- Created mtg_card_schemas.py with MtgCardResponse, MtgCardSearchRequest, etc.
- Added CardImportBatchCreate, CardImportBatchResponse, UserCardImportCreate/Response schemas
- Fixed duplicate UserCardImportRecord class between card_import_batch.py and user_card_import_record.py
- Updated __init__.py with comprehensive schema exports
- Created verify_schemas.py for schema-model matching verification

backend/app/models/user_card_import.py

@@ -1,11 +1,13 @@
 """
 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.
+This model corresponds to the user_card_imports table created in migration 004.
+It stores a user's imported card collection as a JSON array of card names.
 """
-from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Text, UniqueConstraint
+from sqlalchemy import (
+    Column, Integer, String, BigInteger, DateTime, Text,
+    ForeignKey, UniqueConstraint
+)
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql import func
 from app.core.database import Base
@@ -13,21 +15,26 @@ from app.core.database import Base
 
 class UserCardImport(Base):
     """
-    User's imported card collection.
+    User card import record.
     
-    Stores a JSON string of card names that the user owns.
-    Used as the source for building decks from user's actual cards.
+    Stores a user's imported card collection as a JSON array of card names.
+    This table was created in migration 004 and may be superseded by
+    CardImportBatch and UserCardImportRecord in migration 005.
     """
     __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)
+    user_id = Column(Integer, ForeignKey("mtgonline_users.id", ondelete="CASCADE"), nullable=False)
     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")
-
+    
+    __table_args__ = (
+        UniqueConstraint('user_id', name='uq_user_card_imports_user_id'),
+    )
+    
     def __repr__(self) -> str:
         return f"<UserCardImport user={self.user_id}>"