feat: implement QuestionBank CRUD with pagination and template query

- Add pagination support to findAll (page, limit query params)
- Add findByTemplateId method to service
- Add GET /by-template/:templateId endpoint to controller
- Service already includes CRUD for QuestionBank and QuestionBankItem

server/src/assessment/graph/builder.ts

@@ -0,0 +1,77 @@
+import { StateGraph, MemorySaver } from '@langchain/langgraph';
+import { EvaluationAnnotation } from './state';
+import { questionGeneratorNode } from './nodes/generator.node';
+import { interviewerNode } from './nodes/interviewer.node';
+import { graderNode } from './nodes/grader.node';
+import { reportAnalyzerNode } from './nodes/analyzer.node';
+
+/**
+ * Conditional routing logic for the Grader node.
+ */
+const routeAfterGrading = (state: typeof EvaluationAnnotation.State) => {
+  const targetCount = state.questionCount || 5;
+  const questionsLen = state.questions?.length || 0;
+
+  console.log('[Router] Evaluation Result:', {
+    currentIndex: state.currentQuestionIndex,
+    shouldFollowUp: state.shouldFollowUp,
+    numQuestions: questionsLen,
+    targetCount,
+  });
+
+  if (state.shouldFollowUp) {
+    console.log('[Router] Routing to follow-up interviewer');
+    return 'interviewer';
+  }
+
+  if (state.currentQuestionIndex < targetCount) {
+    // If the next question isn't generated yet, go back to generator
+    if (state.currentQuestionIndex >= questionsLen) {
+      console.log('[Router] Index >= Questions, routing to generator');
+      return 'generator';
+    }
+    // If it is generated, go to interviewer
+    console.log('[Router] Index < Questions, routing to interviewer');
+    return 'interviewer';
+  }
+
+  console.log('[Router] Assessment complete, routing to analyzer');
+  return 'analyzer';
+};
+
+/**
+ * Builds and compiles the Evaluation Graph.
+ */
+export const createEvaluationGraph = () => {
+  const workflow = new StateGraph(EvaluationAnnotation)
+    .addNode('generator', questionGeneratorNode)
+    .addNode('interviewer', interviewerNode)
+    .addNode('grader', graderNode)
+    .addNode('analyzer', reportAnalyzerNode)
+
+    // Flow definition
+    .addEdge('__start__', 'generator')
+    .addEdge('generator', 'interviewer')
+
+    // After interviewer, the graph will naturally pause for user input
+    // if we use it in a thread-safe way with interrupts or simple invocation.
+    .addEdge('interviewer', 'grader')
+
+    // After grading, decide where to go
+    .addConditionalEdges('grader', routeAfterGrading, {
+      interviewer: 'interviewer',
+      generator: 'generator',
+      analyzer: 'analyzer',
+    })
+
+    .addEdge('analyzer', '__end__');
+
+  // Using MemorySaver for thread-based persistence
+  const checkpointer = new MemorySaver();
+
+  return workflow.compile({
+    checkpointer,
+    // We want the graph to stop after the interviewer presents the question
+    interruptAfter: ['interviewer'],
+  });
+};