feat: 日志管理 + 质保书生产过程数据图表

- 新增 PlanLog 模型与 /logs API；计划新增/移动/投入生产/生产完成/删除均记录
  (时间/计划号/卷号/操作/状态变化/位置/操作人/说明)
- 新增「日志管理」页面 + 路由 + 导航
- 质保书：把生产完成持久化的实时数据(process_data)按单位分组生成多组柱状图

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/api/__init__.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 from app.api import auth, material, production, plan, downtime, equipment, message, dashboard
-from app.api import prediction, pdi, quality, inspection, cost
+from app.api import prediction, pdi, quality, inspection, cost, logs
 
 router = APIRouter()
 router.include_router(auth.router,        prefix="/auth",       tags=["认证"])
@@ -16,3 +16,4 @@ router.include_router(pdi.router,         prefix="/pdi",        tags=["PDI管理
 router.include_router(quality.router,     prefix="/quality",    tags=["质量管理"])
 router.include_router(inspection.router,  prefix="/inspection", tags=["设备巡检"])
 router.include_router(cost.router,        prefix="/cost",       tags=["成本管理"])
+router.include_router(logs.router,        prefix="/logs",       tags=["日志管理"])