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/key_visits.py

@@ -9,6 +9,7 @@ from app.models.key_visit import KeyVisit
 from app.models.customer import Customer
 from app.models.user import User
 from app.schemas.key_visit import KeyVisitCreate, KeyVisitUpdate, KeyVisitOut
+from app.utils.edit_log import compute_diff, append_entry, init_entry
 
 router = APIRouter(prefix="/key-visits", tags=["KeyVisits"])
 
@@ -27,6 +28,7 @@ async def _enrich(k: KeyVisit, db: AsyncSession) -> dict:
         "planned_visitor": k.planned_visitor,
         "visit_target": k.visit_target,
         "manager_id": str(k.manager_id),
+        "edit_log": k.edit_log or [],
         "manager_name": mgr.scalar_one_or_none(),
     }
 
@@ -63,6 +65,7 @@ async def create_key_visit(
         visit_target=data.visit_target,
         manager_id=uuid.UUID(current_user["user_id"]),
     )
+    init_entry(k, current_user["name"])
     db.add(k)
     await db.commit()
     await db.refresh(k)
@@ -82,9 +85,14 @@ async def update_key_visit(
     if current_user["role"] == "manager" and str(k.manager_id) != current_user["user_id"]:
         raise HTTPException(status_code=403, detail="Access denied")
 
+    old_snapshot = {"customer_id": str(k.customer_id), "urgency_level": k.urgency_level, "description": k.description, "progress_status": k.progress_status, "planned_date": k.planned_date, "planned_visitor": k.planned_visitor, "visit_target": k.visit_target}
     update_data = data.model_dump(exclude_unset=True)
     for key, v in update_data.items():
         setattr(k, key, v)
+    new_snapshot = {"customer_id": str(k.customer_id), "urgency_level": k.urgency_level, "description": k.description, "progress_status": k.progress_status, "planned_date": k.planned_date, "planned_visitor": k.planned_visitor, "visit_target": k.visit_target}
+    changes = compute_diff(old_snapshot, new_snapshot)
+    if changes:
+        append_entry(k, current_user["name"], changes, getattr(data, "edit_reason", None))
     await db.commit()
     await db.refresh(k)
     return await _enrich(k, db)