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/alembic/env.py

@@ -25,6 +25,7 @@ from app.models.user_data import (
     NetworkMember, UserPreference, UserActivityLog
 )
 from app.models.user_deck import UserDeck, UserDeckCard, DeckPrecedent, DeckPrecedentCard, CardSuggestion
+from app.models.user_card_import import UserCardImport
 
 # this is the Alembic Config object
 config = context.config

backend/alembic/versions/004_card_import_table.py

@@ -0,0 +1,36 @@
+"""
+Alembic migration: Create user_card_imports table.
+
+This migration adds the user_card_imports table which stores
+a user's imported card collection as a JSON array of card names.
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '004'
+down_revision = '003'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    """Create user_card_imports table."""
+    op.create_table(
+        'user_card_imports',
+        sa.Column('id', sa.Integer(), autoincrement=True, nullable=False),
+        sa.Column('user_id', sa.Integer(), nullable=False),
+        sa.Column('card_names_json', sa.Text(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), server_default=sa.func.now()),
+        sa.Column('updated_at', sa.DateTime(), server_default=sa.func.now(), onupdate=sa.func.now()),
+        sa.PrimaryKeyConstraint('id'),
+        sa.ForeignKeyConstraint(['user_id'], ['mtgonline_users.id'], ondelete='CASCADE'),
+        sa.UniqueConstraint('user_id', name='uq_user_card_imports_user_id'),
+        sa.Index('idx_user_card_imports_user', 'user_id'),
+    )
+
+
+def downgrade() -> None:
+    """Drop user_card_imports table."""
+    op.drop_table('user_card_imports')