fix: preserve nullable cloud task bindings

backend/alembic/env.py

@@ -18,6 +18,7 @@
 # Import app configuration and models
 from app.core.config import settings
 from app.db.base import Base
+from app.db.mysql_loop_items_schema import normalize_mysql_loop_items_schema
 from app.db.timezone import MYSQL_SESSION_TIMEZONE_OFFSET
 
 # Import all models to ensure they are registered with SQLAlchemy
@@ -138,6 +139,7 @@ def _initialize_fresh_database(connection) -> None:
     # This is cross-database compatible (works for both MySQL and SQLite)
     logger.info("Creating all tables using SQLAlchemy metadata...")
     Base.metadata.create_all(bind=connection, checkfirst=True)
+    normalize_mysql_loop_items_schema(connection)
     logger.info("All tables created successfully")
 
     # Step 2: Create alembic_version table and stamp to head

backend/alembic/versions/20260804_c0d1e2f3a4b5_align_mysql_loop_items_schema.py

@@ -0,0 +1,31 @@
+"""Align MySQL loop items with the production sentinel schema.
+
+Revision ID: c0d1e2f3a4b5
+Revises: b9c0d1e2f3a4
+Create Date: 2026-08-04
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+from app.db.mysql_loop_items_schema import (
+    normalize_mysql_loop_items_schema,
+    restore_nullable_mysql_loop_items_schema,
+)
+
+revision: str = "c0d1e2f3a4b5"
+down_revision: Union[str, Sequence[str], None] = "b9c0d1e2f3a4"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Use sentinel values and generated unique projections on MySQL."""
+
+    normalize_mysql_loop_items_schema(op.get_bind())
+
+
+def downgrade() -> None:
+    """Restore nullable columns, direct unique indexes, and foreign keys."""
+
+    restore_nullable_mysql_loop_items_schema(op.get_bind())