feat(measure): memorizza tempo di inserimento misura (input_duration_ms)

Colonna nullable su measurements + migration 003, campo opzionale negli
schemi API (create singola e batch), passthrough nel proxy Flask e timer
lato client in task_execute: parte all'attivazione del subtask, si
resetta su auto-advance e navigazione manuale.

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

src/backend/api/routers/measurements.py

@@ -46,6 +46,7 @@ async def create_measurement(
             lot_number=data.lot_number,
             serial_number=data.serial_number,
             input_method=data.input_method,
+            input_duration_ms=data.input_duration_ms,
         )
         return MeasurementResponse.model_validate(measurement)
     except ValueError as e:
@@ -74,6 +75,7 @@ async def create_measurement_batch(
                 lot_number=measurement_data.lot_number,
                 serial_number=measurement_data.serial_number,
                 input_method=measurement_data.input_method,
+                input_duration_ms=measurement_data.input_duration_ms,
             )
             measurements.append(measurement)
         return [MeasurementResponse.model_validate(m) for m in measurements]