feat: add theme preset system with admin CRUD, public listing, and user theme settings

- Add ChromaticColor (17 Tailwind colors) and NeutralColor (5 grays) enums
- Add ThemePreset table with flat color columns and unique name constraint
- Add admin theme endpoints (CRUD + set default) at /api/v1/admin/theme
- Add public theme listing at /api/v1/site/themes
- Add user theme settings (PATCH /theme) with color snapshot on User model
- User.color_* columns store per-user overrides; fallback to default preset then builtin
- Initialize default theme preset in migration
- Remove legacy defaultTheme/themes settings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sqlmodels/report.py

@@ -1,5 +1,6 @@
 from enum import StrEnum
 from typing import TYPE_CHECKING
+from uuid import UUID
 
 from sqlmodel import Field, Relationship
 
@@ -24,7 +25,7 @@ class Report(SQLModelBase, TableBaseMixin):
     description: str | None = Field(default=None, max_length=255, description="补充描述")
     
     # 外键
-    share_id: int = Field(
+    share_id: UUID = Field(
         foreign_key="share.id",
         index=True,
         ondelete="CASCADE"