feat(vision): il server esegue tramite worker e salva misure vere

Aggiunge POST /api/vision/execute: route l'immagine al worker di visione,
mappa le uscite del grafo sulle quote e le salva con save_measurement -
stesso verdetto, stesso gate del fuori tolleranza di ogni altra misura.
Nuova tabella vision_results (una riga per acquisizione, non per quota) e
input_method 'camera' su measurements.

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

src/backend/models/orm/vision.py

@@ -0,0 +1,40 @@
+"""One row per vision execution - not per quote."""
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy import DateTime, Enum, ForeignKey, Integer, JSON, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from src.backend.database import Base
+
+
+class VisionResult(Base):
+    __tablename__ = "vision_results"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    task_id: Mapped[int] = mapped_column(
+        Integer, ForeignKey("recipe_tasks.id"), nullable=False, index=True
+    )
+    image_path: Mapped[Optional[str]] = mapped_column(String(500), nullable=True)
+    overlay_path: Mapped[Optional[str]] = mapped_column(String(500), nullable=True)
+    engine_version: Mapped[str] = mapped_column(String(64), nullable=False)
+    executed_on: Mapped[str] = mapped_column(
+        Enum("server", "station", name="vision_executed_on_enum"), nullable=False
+    )
+    station_id: Mapped[Optional[int]] = mapped_column(
+        Integer, ForeignKey("stations.id"), nullable=True
+    )
+    device_code: Mapped[Optional[str]] = mapped_column(String(100), nullable=True)
+    # Copied, not referenced: a calibration redone six months from now must not
+    # rewrite what a measurement already taken means. Same for the graph.
+    calibration_snapshot: Mapped[Optional[dict]] = mapped_column(JSON, nullable=True)
+    graph_snapshot: Mapped[dict] = mapped_column(JSON, nullable=False)
+    duration_ms: Mapped[Optional[int]] = mapped_column(Integer, nullable=True)
+    executed_at: Mapped[datetime] = mapped_column(
+        DateTime, nullable=False, server_default=func.now()
+    )
+
+    __table_args__ = ({"mysql_engine": "InnoDB", "mysql_charset": "utf8mb4"},)
+
+    def __repr__(self) -> str:
+        return f"<VisionResult task={self.task_id} engine={self.engine_version}>"