Backend: UTC nel DB, +00:00 nelle API, ora italiana solo in presentazione (#42)

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

src/backend/models/api/production.py

@@ -1,5 +1,5 @@
 """Pydantic schemas for production runs and their events."""
-from datetime import datetime
+from src.backend.models.api.tipi import UtcDateTime
 from typing import Literal, Optional
 
 from pydantic import BaseModel, ConfigDict, Field
@@ -21,7 +21,7 @@ class ProductionEventResponse(BaseModel):
     supervisor_id: Optional[int]
     task_id: Optional[int] = None
     note: Optional[str]
-    created_at: datetime
+    created_at: UtcDateTime
 
 
 class ProductionRunResponse(BaseModel):
@@ -36,11 +36,11 @@ class ProductionRunResponse(BaseModel):
     serial_number: Optional[str]
     status: str
     measurement_interval_minutes: Optional[int]
-    next_measurement_at: Optional[datetime]
+    next_measurement_at: Optional[UtcDateTime]
     cycle_count: int
-    started_at: datetime
-    paused_at: Optional[datetime]
-    closed_at: Optional[datetime]
+    started_at: UtcDateTime
+    paused_at: Optional[UtcDateTime]
+    closed_at: Optional[UtcDateTime]
     closed_by: Optional[int]
     statistics_path: Optional[str] = None
 
@@ -49,7 +49,7 @@ class ProductionRunResponse(BaseModel):
     # overdue is a fact the operator must see, not deduce.
     seconds_to_next_measurement: Optional[int] = None
     overdue: bool = False
-    server_time: Optional[datetime] = None
+    server_time: Optional[UtcDateTime] = None
 
     # The measurement tasks of this run's version, in execution order. The client
     # needs them to bring the operator back to the measurement when the interval