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/schemas.py

@@ -3,8 +3,9 @@ from __future__ import annotations
 from datetime import datetime
 from typing import ClassVar
 from uuid import UUID
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
-from pydantic import BaseModel, ConfigDict, EmailStr, Field
+from pydantic import BaseModel, ConfigDict, EmailStr, Field, field_validator
 
 from schemas.inbox.messages import (
     CalendarContent,
@@ -49,9 +50,27 @@ class ScheduleItemCreateRequest(BaseModel):
     description: str | None = Field(default=None, max_length=2000)
     start_at: datetime
     end_at: datetime | None = None
-    timezone: str = Field(default="UTC", max_length=50)
+    timezone: str = Field(..., min_length=1, max_length=50)
     metadata: ScheduleItemMetadata | None = None
 
+    @field_validator("timezone")
+    @classmethod
+    def validate_timezone(cls, value: str) -> str:
+        try:
+            ZoneInfo(value)
+        except ZoneInfoNotFoundError as exc:
+            raise ValueError("timezone must be a valid IANA timezone") from exc
+        return value
+
+    @field_validator("start_at", "end_at")
+    @classmethod
+    def validate_datetime_tzinfo(cls, value: datetime | None) -> datetime | None:
+        if value is None:
+            return None
+        if value.tzinfo is None:
+            raise ValueError("datetime must include timezone offset")
+        return value
+
 
 class ScheduleItemUpdateRequest(BaseModel):
     model_config: ClassVar[ConfigDict] = ConfigDict(extra="forbid")
@@ -64,6 +83,26 @@ class ScheduleItemUpdateRequest(BaseModel):
     metadata: ScheduleItemMetadata | None = None
     status: ScheduleItemStatus | None = None
 
+    @field_validator("timezone")
+    @classmethod
+    def validate_timezone(cls, value: str | None) -> str | None:
+        if value is None:
+            return None
+        try:
+            ZoneInfo(value)
+        except ZoneInfoNotFoundError as exc:
+            raise ValueError("timezone must be a valid IANA timezone") from exc
+        return value
+
+    @field_validator("start_at", "end_at")
+    @classmethod
+    def validate_datetime_tzinfo(cls, value: datetime | None) -> datetime | None:
+        if value is None:
+            return None
+        if value.tzinfo is None:
+            raise ValueError("datetime must include timezone offset")
+        return value
+
 
 class ScheduleItemResponse(BaseModel):
     model_config: ClassVar[ConfigDict] = ConfigDict(from_attributes=True)
@@ -99,6 +138,13 @@ class ScheduleItemListRequest(BaseModel):
     start_at: datetime
     end_at: datetime
 
+    @field_validator("start_at", "end_at")
+    @classmethod
+    def validate_datetime_tzinfo(cls, value: datetime) -> datetime:
+        if value.tzinfo is None:
+            raise ValueError("datetime must include timezone offset")
+        return value
+
 
 _PERMISSION_VIEW = 1
 _PERMISSION_INVITE = 2