feat: 信息架构重组 + 变更追踪 + 图片预览增强

- 信息架构重组: 周报精简为拜访+纪要两个Tab，工作计划/商机/要客独立为侧边栏「工作」分组下的独立页面
- 侧边栏分组: 汇总/工作/管理三层分组，仪表盘四卡可点击跳转
- 变更追踪(edit_log): 5张表新增JSONB edit_log列，POST创建/PUT diff自动记录，编辑弹窗变更时间轴，表格🕐编辑标记
- 图片预览增强: ImagePreview统一组件，支持适应页面/缩放/拖拽平移/滚轮缩放/键盘快捷键
- 修复客户导入500错误(errors变量未初始化)
- 移除工作计划/商机/要客页面冗余编辑按钮

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

backend/app/api/work_plans.py

@@ -7,6 +7,7 @@ from sqlalchemy import select
 from app.database import get_db
 from app.middleware.auth import get_current_user, require_any_role
 from app.utils.timezone import parse_date
+from app.utils.edit_log import compute_diff, append_entry, init_entry
 from app.models.work_plan import WorkPlan
 from app.models.customer import Customer
 from app.models.user import User
@@ -27,6 +28,7 @@ async def _enrich(wp: WorkPlan, db: AsyncSession) -> dict:
         "manager_id": str(wp.manager_id),
         "manager_name": mgr.scalar_one_or_none(),
         "status": wp.status,
+        "edit_log": wp.edit_log or [],
     }
 
 
@@ -59,6 +61,7 @@ async def create_work_plan(
         manager_id=uuid.UUID(current_user["user_id"]),
         status=data.status,
     )
+    init_entry(wp, current_user["name"])
     db.add(wp)
     await db.commit()
     await db.refresh(wp)
@@ -78,11 +81,16 @@ async def update_work_plan(
     if current_user["role"] == "manager" and str(wp.manager_id) != current_user["user_id"]:
         raise HTTPException(status_code=403, detail="Access denied")
 
+    old_snapshot = {"customer_id": str(wp.customer_id), "plan_content": wp.plan_content, "plan_date": str(wp.plan_date), "status": wp.status}
     update_data = data.model_dump(exclude_unset=True)
     if "plan_date" in update_data and update_data["plan_date"]:
         update_data["plan_date"] = parse_date(update_data["plan_date"])
     for k, v in update_data.items():
         setattr(wp, k, v)
+    new_snapshot = {"customer_id": str(wp.customer_id), "plan_content": wp.plan_content, "plan_date": str(wp.plan_date), "status": wp.status}
+    changes = compute_diff(old_snapshot, new_snapshot)
+    if changes:
+        append_entry(wp, current_user["name"], changes, getattr(data, "edit_reason", None))
     await db.commit()
     await db.refresh(wp)
     return await _enrich(wp, db)