feat: 历史周报+图片预览+照片管理+导入优化+用户合并

新增:
- 历史周报: Dashboard/周报详情支持周选择器翻看往周，归档只读
- 图片预览: 全屏大图(移动端+PC端)，点击遮罩关闭
- PC端照片管理: 编辑时可上传/删除照片
- 客户导入改为更新模式: 重名自动更新信息，显示操作明细
- 导入跳过原因: 旧周报导入也显示每条跳过原因

优化:
- 填报进度权限: 经理只看到自己，支局长/领导看全员
- 客户经理暖灰色hash标签列
- 用户去重合并(4组)，数据完整迁移
- CLAUDE.md 更新到最新状态

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

backend/app/api/export.py

@@ -1,4 +1,6 @@
-from fastapi import APIRouter, Depends
+from typing import Optional
+from datetime import date
+from fastapi import APIRouter, Depends, Query
 from fastapi.responses import StreamingResponse
 from sqlalchemy.ext.asyncio import AsyncSession
 from app.database import get_db
@@ -10,11 +12,13 @@ router = APIRouter(prefix="/export", tags=["Export"])
 
 @router.get("/weekly-report")
 async def download_weekly_report(
+    reference_date: Optional[str] = Query(None),
     current_user: dict = Depends(require_director_or_leader),
     db: AsyncSession = Depends(get_db),
 ):
-    """Export this week's report as a 4-sheet .xlsx file."""
-    excel_bytes = await export_weekly_report(db)
+    """Export week report as 4-sheet .xlsx. Pass reference_date for historical weeks."""
+    ref = date.fromisoformat(reference_date) if reference_date else None
+    excel_bytes = await export_weekly_report(db, ref)
     return StreamingResponse(
         excel_bytes,
         media_type="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",