fix(migrations): riparenta input_duration dopo 003_measurement_interval

Il rebase aveva creato due head Alembic (003_input_duration e
003_measurement_interval entrambi figli di 002): upgrade head all'avvio
del server sarebbe fallito. Rinominata la revision in 004_input_duration
con down_revision 003_measurement_interval — catena di nuovo lineare.

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

src/backend/migrations/versions/004_add_input_duration_ms.py

@@ -1,7 +1,7 @@
 """add input_duration_ms to measurements
 
-Revision ID: 003_input_duration
+Revision ID: 004_input_duration
-Revises: 002_add_stations
+Revises: 003_measurement_interval
 Create Date: 2026-07-28
 
 """
@@ -10,8 +10,8 @@ from typing import Sequence, Union
 from alembic import op
 import sqlalchemy as sa
 
-revision: str = '003_input_duration'
+revision: str = '004_input_duration'
-down_revision: Union[str, None] = '002_add_stations'
+down_revision: Union[str, None] = '003_measurement_interval'
 branch_labels: Union[str, Sequence[str], None] = None
 depends_on: Union[str, Sequence[str], None] = None