feat(similarity): add document similarity detection with embeddings and cosine similarity

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

migrations/versions/009_add_embedding_column.py

@@ -0,0 +1,27 @@
+"""Add embedding column to files table for document similarity
+
+Revision ID: 009_add_embedding_column
+Revises: 008_add_performance_indexes
+Create Date: 2026-03-01
+
+"""
+
+from typing import Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "009_add_embedding_column"
+down_revision: Union[str, None] = "008_add_performance_indexes"
+depends_on: Union[str, None] = None
+
+
+def upgrade() -> None:
+    """Add embedding column to files table for storing text embedding vectors."""
+    op.add_column("files", sa.Column("embedding", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove embedding column from files table."""
+    op.drop_column("files", "embedding")