feat(api): register knowledge graph routes in API index (SSC-11)

Mount knowledge graph routes at /api/knowledge-graph endpoint

Author: Sakeeb91

apps/api/src/index.ts

@@ -7,6 +7,7 @@ import authRoutes from './routes/auth.routes';
 import uploadRoutes from './routes/upload.routes';
 import flashcardRoutes from './routes/flashcard.routes';
 import quizRoutes from './routes/quiz.routes';
+import knowledgeGraphRoutes from './routes/knowledgeGraph.routes';
 
 // Load environment variables
 dotenv.config();
@@ -51,6 +52,9 @@ app.use('/api/flashcards', flashcardRoutes);
 // Quiz routes with AI generation
 app.use('/api/quizzes', quizRoutes);
 
+// Knowledge Graph routes with AI extraction
+app.use('/api/knowledge-graph', knowledgeGraphRoutes);
+
 // Error handling middleware
 app.use((err: Error, _req: Request, res: Response, _next: NextFunction) => {
   console.error(err.stack);