Migrazione 016 vision_recipe_dir, copy-on-write, dxf_compare tra i task di misura (#46)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/backend/migrations/versions/016_vision_recipe_dir.py

@@ -0,0 +1,30 @@
+"""recipe_tasks.vision_recipe_dir: cartella della ricetta VisionSuite v2 (#46)
+
+Percorso relativo sotto upload_path della cartella immutabile che contiene
+recipe.json e i file di meta (DXF, modelli .npz, ...).
+
+Revision ID: 016_vision_recipe_dir
+Revises: 015_api_key_hash
+Create Date: 2026-10-07
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '016_vision_recipe_dir'
+down_revision: Union[str, None] = '015_api_key_hash'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # batch: SQLite non sa fare DROP COLUMN nativo su tutte le versioni
+    with op.batch_alter_table('recipe_tasks') as batch:
+        batch.add_column(sa.Column('vision_recipe_dir', sa.String(500), nullable=True))
+
+
+def downgrade() -> None:
+    with op.batch_alter_table('recipe_tasks') as batch:
+        batch.drop_column('vision_recipe_dir')