Replace box picker with free-text location in audit scan

"Where found" during inventory audit is now a plain text field
(e.g. "каб. 305") stored on the object instead of assigning it to a
box, since audit walks often use room/office labels that don't map
to the box/shelf hierarchy used elsewhere. Box assignment via the
regular object form is unaffected.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/alembic/versions/e7a2c9f1b3d4_add_last_seen_location_to_objects.py

@@ -0,0 +1,30 @@
+"""add last_seen_location to objects
+
+Revision ID: e7a2c9f1b3d4
+Revises: c3bc00a214e0
+Create Date: 2026-07-22 12:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'e7a2c9f1b3d4'
+down_revision: Union[str, None] = 'c3bc00a214e0'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('objects', sa.Column('last_seen_location', sa.String(length=255), nullable=True))
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('objects', 'last_seen_location')
+    # ### end Alembic commands ###