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/services/measurement_service.py

@@ -48,6 +48,7 @@ async def save_measurement(
     lot_number: str | None = None,
     serial_number: str | None = None,
     input_method: str = "manual",
+    input_duration_ms: int | None = None,
 ) -> Measurement:
     """Save a single measurement with auto-calculated pass/fail."""
     # Get subtask for tolerance values
@@ -70,6 +71,7 @@ async def save_measurement(
         lot_number=lot_number,
         serial_number=serial_number,
         input_method=input_method,
+        input_duration_ms=input_duration_ms,
     )
     db.add(measurement)
     await db.flush()