feat: 添加日历批量操作与客户端时区感知功能，优化前端 UI 交互体验

backend/src/v1/schedule_items/service.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from datetime import datetime, timezone
 from typing import TYPE_CHECKING, Protocol, Literal
 from uuid import UUID
 
@@ -83,15 +84,18 @@ class ScheduleItemService(BaseService):
     ) -> ScheduleItemResponse:
         user_id = self.require_user_id()
 
-        if request.end_at and request.end_at <= request.start_at:
+        normalized_start_at = self._to_utc_required(request.start_at)
+        normalized_end_at = self._to_utc(request.end_at)
+
+        if normalized_end_at and normalized_end_at <= normalized_start_at:
             raise HTTPException(status_code=400, detail="end_at must be after start_at")
 
         data = {
             "owner_id": user_id,
             "title": request.title,
             "description": request.description,
-            "start_at": request.start_at,
-            "end_at": request.end_at,
+            "start_at": normalized_start_at,
+            "end_at": normalized_end_at,
             "timezone": request.timezone,
             "extra_metadata": request.metadata.model_dump() if request.metadata else {},
             "source_type": source_type,
@@ -168,10 +172,21 @@ class ScheduleItemService(BaseService):
             # Validate time range
             next_start = update_data.get("start_at", existing.start_at)
             next_end = update_data.get("end_at", existing.end_at)
-            if next_end is not None and next_end <= next_start:
-                raise HTTPException(
-                    status_code=400, detail="end_at must be after start_at"
-                )
+            if isinstance(next_start, datetime):
+                next_start = self._to_utc_required(next_start)
+                update_data["start_at"] = next_start
+            if isinstance(next_end, datetime):
+                next_end = self._to_utc(next_end)
+                update_data["end_at"] = next_end
+            if next_end is not None:
+                if not isinstance(next_start, datetime):
+                    raise HTTPException(
+                        status_code=400, detail="start_at must include timezone"
+                    )
+                if next_end <= next_start:
+                    raise HTTPException(
+                        status_code=400, detail="end_at must be after start_at"
+                    )
 
             if not update_data:
                 return self._to_response(existing)
@@ -218,13 +233,16 @@ class ScheduleItemService(BaseService):
     ) -> list[ScheduleItemResponse]:
         user_id = self.require_user_id()
 
-        if request.end_at <= request.start_at:
+        normalized_start_at = self._to_utc_required(request.start_at)
+        normalized_end_at = self._to_utc_required(request.end_at)
+
+        if normalized_end_at <= normalized_start_at:
             raise HTTPException(status_code=400, detail="end_at must be after start_at")
 
         try:
             subscribed_items = (
                 await self._repository.list_subscribed_items_by_date_range(
-                    user_id, request.start_at, request.end_at
+                    user_id, normalized_start_at, normalized_end_at
                 )
             )
 
@@ -518,3 +536,18 @@ class ScheduleItemService(BaseService):
 
         if subscriptions:
             await self._session.commit()
+
+    def _to_utc(self, dt: datetime | None) -> datetime | None:
+        if dt is None:
+            return None
+        if dt.tzinfo is None:
+            raise HTTPException(
+                status_code=400, detail="datetime must include timezone"
+            )
+        return dt.astimezone(timezone.utc)
+
+    def _to_utc_required(self, dt: datetime) -> datetime:
+        normalized = self._to_utc(dt)
+        if normalized is None:
+            raise HTTPException(status_code=400, detail="datetime is required")
+        return normalized