feat: v2.0 — maintenance module, AI analysis, station power fix

- Add full 检修维护中心 (6.4): 3-type work orders (消缺/巡检/抄表),
  asset management, warehouse, work plans, billing settlement
- Add AI智能分析 tab with LLM-powered diagnostics (StepFun + ZhipuAI)
- Add AI模型配置 settings page (provider, temperature, prompts)
- Fix station power accuracy: use API station total (station_power)
  instead of inverter-level computation — eliminates timing gaps
- Add 7 new DB models, 4 new API routers, 5 new frontend pages
- Migrations: 009 (maintenance expansion) + 010 (AI analysis)
- Version bump: 1.6.1 → 2.0.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/backend/app/api/router.py

@@ -1,5 +1,5 @@
 from fastapi import APIRouter
-from app.api.v1 import auth, users, devices, energy, monitoring, alarms, reports, carbon, dashboard, collectors, websocket, audit, settings, charging, quota, cost, maintenance, management, prediction, energy_strategy, weather, ai_ops, branding, version, kpi
+from app.api.v1 import auth, users, devices, energy, monitoring, alarms, reports, carbon, dashboard, collectors, websocket, audit, settings, charging, quota, cost, maintenance, management, prediction, energy_strategy, weather, ai_ops, branding, version, kpi, assets, warehouse, work_plans, billing
 
 api_router = APIRouter(prefix="/api/v1")
 
@@ -28,3 +28,7 @@ api_router.include_router(ai_ops.router)
 api_router.include_router(branding.router)
 api_router.include_router(version.router)
 api_router.include_router(kpi.router)
+api_router.include_router(assets.router)
+api_router.include_router(warehouse.router)
+api_router.include_router(work_plans.router)
+api_router.include_router(billing.router)