refactor: update database migration strategy and schema creation (#79)

- Modified the `init_db` function to let Alembic handle schema creation, removing the explicit schema creation step.
- Updated the `migrate_canvas_data` migration to depend on the new `create_schema` migration, ensuring proper order of operations.
- Introduced a new migration file `create_schema.py` to explicitly create the database schema, improving migration reliability.

Author: atyrode

src/backend/database/database.py

@@ -184,9 +184,8 @@ async def run_migrations() -> None:
 
 async def init_db() -> None:
     """Initialize the database with required tables"""
-    # Create schema and tables
+    # Only create tables, let Alembic handle schema creation
     async with engine.begin() as conn:
-        await conn.execute(CreateSchema(SCHEMA_NAME, if_not_exists=True))
         await conn.run_sync(Base.metadata.create_all)
 
 async def get_session() -> AsyncGenerator[AsyncSession, None]:

src/backend/database/migrations/versions/2025_05_02_2055-migrate_canvas_data.py

@@ -17,7 +17,7 @@
 
 # revision identifiers, used by Alembic.
 revision = 'migrate_canvas_data'
-down_revision = None
+down_revision = 'create_schema'  # This migration depends on the schema creation
 branch_labels = None
 depends_on = None
 

src/backend/database/migrations/versions/2025_05_04_2310-create_schema.py

@@ -0,0 +1,46 @@
+"""Create schema explicitly
+
+Revision ID: create_schema
+Revises: 
+Create Date: 2025-05-04 23:10:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+# Import the schema name from the models using dynamic import
+import importlib.util
+import os
+
+# Get the absolute path to the base_model module
+base_model_path = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))), "models", "base_model.py")
+
+# Load the module dynamically
+spec = importlib.util.spec_from_file_location("base_model", base_model_path)
+base_model = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(base_model)
+
+# Get SCHEMA_NAME from the loaded module
+SCHEMA_NAME = base_model.SCHEMA_NAME
+
+# revision identifiers, used by Alembic.
+revision: str = 'create_schema'
+down_revision: Union[str, None] = None  # This is the first migration
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Create schema explicitly before other operations."""
+    # Create schema using execute() with a SQL string instead of CreateSchema
+    # This approach can be more reliable in certain PostgreSQL versions
+    op.execute(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA_NAME}")
+
+
+def downgrade() -> None:
+    """Drop schema if needed."""
+    # We don't actually want to drop the schema on downgrade
+    # as it would delete all data, but the function is required
+    pass