chore: backup before code cleanup

Backup commit before executing remove-unused-code proposal.
This includes all pending changes and new features.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/alembic/versions/f1a2b3c4d5e6_fix_sessions_schema_mismatch.py

@@ -0,0 +1,53 @@
+"""fix_sessions_schema_mismatch
+
+Revision ID: f1a2b3c4d5e6
+Revises: e51c9a16ee16
+Create Date: 2025-12-10 10:30:00.000000
+
+Fix schema mismatch between SQLAlchemy model and MySQL database:
+1. Remove session_token column from tool_ocr_sessions (not in model)
+2. Remove is_active column from tool_ocr_sessions (not in model)
+3. Note: processing_track in tool_ocr_tasks is nullable so it won't cause issues
+
+These columns were added to the database manually or by another migration
+but are not present in the current SQLAlchemy models.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import mysql
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'f1a2b3c4d5e6'
+down_revision: Union[str, None] = 'e51c9a16ee16'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """
+    Remove columns from tool_ocr_sessions that exist in DB but not in model.
+    This fixes the "Field 'session_token' doesn't have a default value" error.
+    """
+    # Remove session_token column (exists in DB, not in model)
+    op.drop_column('tool_ocr_sessions', 'session_token')
+
+    # Remove is_active column (exists in DB, not in model)
+    op.drop_column('tool_ocr_sessions', 'is_active')
+
+
+def downgrade() -> None:
+    """
+    Re-add the columns if needed to rollback.
+    """
+    # Re-add is_active column
+    op.add_column('tool_ocr_sessions',
+        sa.Column('is_active', mysql.TINYINT(), nullable=False, server_default='1',
+                  comment='Whether the session is active'))
+
+    # Re-add session_token column
+    op.add_column('tool_ocr_sessions',
+        sa.Column('session_token', sa.String(length=255), nullable=False,
+                  comment='Session token for authentication'))