PIN a 4 cifre: migrazione 017, login-pin, pin-users, PUT pin, capoturno via PIN (#59)

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

src/backend/migrations/versions/017_user_pin.py

@@ -0,0 +1,34 @@
+"""users: PIN a 4 cifre per login rapido e capoturno (#59)
+
+pin_hash (bcrypt, mai in chiaro), contatore errori consecutivi e fine blocco.
+
+Revision ID: 017_user_pin
+Revises: 016_vision_recipe_dir
+Create Date: 2026-10-07
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = '017_user_pin'
+down_revision: Union[str, None] = '016_vision_recipe_dir'
+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('users') as batch:
+        batch.add_column(sa.Column('pin_hash', sa.String(255), nullable=True))
+        batch.add_column(sa.Column(
+            'pin_failed_count', sa.Integer(), nullable=False, server_default='0'))
+        batch.add_column(sa.Column('pin_locked_until', sa.DateTime(), nullable=True))
+
+
+def downgrade() -> None:
+    with op.batch_alter_table('users') as batch:
+        batch.drop_column('pin_locked_until')
+        batch.drop_column('pin_failed_count')
+        batch.drop_column('pin_hash')