docs(vision): commenta perché camera resta fuori dal pattern client

MeasurementCreate.input_method accetta solo usb_caliper|manual anche se
l'enum ORM e il database permettono ormai camera. È voluto: una misura
da camera deve nascere in vision_service.execute_task, mai da un client
che posta JSON direttamente - non c'è dietro né immagine, né grafo, né
engine_version. Commento aggiunto perché non venga "corretto" tornando
alla lettera dell'enum.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014BBnuACZSCJqXrMYC3LUMU

src/backend/models/api/measurement.py

@@ -12,6 +12,11 @@ class MeasurementCreate(BaseModel):
     value: float
     lot_number: Optional[str] = Field(None, max_length=100)
     serial_number: Optional[str] = Field(None, max_length=100)
+    # "camera" is deliberately absent from this pattern, even though the ORM
+    # enum and the database allow it. Do not add it here: a camera
+    # measurement must be produced by vision_service.execute_task, never by a
+    # client posting JSON straight to this endpoint - there is no image, no
+    # graph and no engine_version behind a value that arrived this way.
     input_method: str = Field("manual", pattern="^(usb_caliper|manual)$")
     input_duration_ms: Optional[int] = Field(None, ge=0)
     # The production this belongs to, when one is open at the station.