feat: string monitoring, ROI simulator, knowledge base, stubs (v1.6.0)

New functional pages:
- String-Level Monitoring — simulated string data with heatmap,
  comparison chart, status table (Under Construction banner)
- ROI Simulator — 25-year investment return calculator with
  IRR, NPV, payback period, cash flow chart
- Knowledge Base — O&M wiki with 5 articles, search, categories
- Mobile responsive — sidebar auto-collapse on small screens

Under Construction stubs:
- I-V Curve Diagnosis — demo chart, 4 feature preview cards
- Remote Device Configuration — parameter preview, disabled
  actions, v2.0+ roadmap timeline

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

frontend/src/App.tsx

@@ -23,8 +23,13 @@ import DataQuery from './pages/DataQuery';
 import Management from './pages/Management';
 import Prediction from './pages/Prediction';
 import EnergyStrategy from './pages/EnergyStrategy';
+import ROISimulator from './pages/ROISimulator';
 import AIOperations from './pages/AIOperations';
+import KnowledgeBase from './pages/KnowledgeBase';
 import BigScreen from './pages/BigScreen';
+import StringMonitoring from './pages/StringMonitoring';
+import IVDiagnosis from './pages/IVDiagnosis';
+import RemoteConfig from './pages/RemoteConfig';
 
 import { isLoggedIn } from './utils/auth';
 
@@ -66,7 +71,12 @@ function AppContent() {
             <Route path="management" element={<Management />} />
             <Route path="prediction" element={<Prediction />} />
             <Route path="energy-strategy" element={<EnergyStrategy />} />
+            <Route path="roi-simulator" element={<ROISimulator />} />
             <Route path="ai-operations" element={<AIOperations />} />
+            <Route path="knowledge-base" element={<KnowledgeBase />} />
+            <Route path="string-monitoring" element={<StringMonitoring />} />
+            <Route path="iv-diagnosis" element={<IVDiagnosis />} />
+            <Route path="remote-config" element={<RemoteConfig />} />
             <Route path="system/*" element={<SystemManagement />} />
           </Route>
         </Routes>