Visione: quota non prodotta salvata come NaN (value NULL, fail) invece del 422; migrazione 022

Refs #118

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

src/backend/services/measurement_service.py

@@ -302,7 +302,7 @@ async def current_cycle_measurements(
     return [
         {
             "subtask_id": m.subtask_id,
-            "value": float(m.value),
+            "value": float(m.value) if m.value is not None else None,  # #118: NaN
             "pass_fail": m.pass_fail,
             "measured_at": m.measured_at,
         }
@@ -355,7 +355,7 @@ async def save_measurement(
     subtask_id: int,
     version_id: int,
     measured_by: int,
-    value: float,
+    value: float | None,
     lot_number: str | None = None,
     serial_number: str | None = None,
     input_method: str = "manual",
@@ -372,8 +372,12 @@ async def save_measurement(
     batch of quotes taken at the same instant (see Ruling R10 / vision_service):
     the gate models "moving on" between measurements taken one after another,
     which does not exist inside a single camera acquisition.
+
+    #118: ``value=None`` is a quote the vision graph did not produce (shown as
+    NaN): saved as a ``fail`` with no deviation. Only the vision path passes it.
     """
-    _validate_measured_value(value)
+    if value is not None:  # #118: una quota non misurata non ha un valore da validare
+        _validate_measured_value(value)
 
     # Get subtask for tolerance values
     result = await db.execute(
@@ -421,8 +425,12 @@ async def save_measurement(
     # Rounded once, here, so the stored value is exactly the one the verdict
     # above was computed on - calculate_pass_fail rounds internally too, but
     # matching it here keeps the persisted row from disagreeing with itself.
-    value = round(value, 6)
-    pass_fail, deviation = calculate_pass_fail(value, subtask)
+    if value is None:
+        # #118: quota non prodotta dal grafo -> NaN: fail, nessuna deviazione
+        pass_fail, deviation = "fail", None
+    else:
+        value = round(value, 6)
+        pass_fail, deviation = calculate_pass_fail(value, subtask)
 
     measurement = Measurement(
         subtask_id=subtask_id,