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/ocr/ocr.service.ts

@@ -0,0 +1,80 @@
+import { Injectable, Logger } from '@nestjs/common';
+import { createWorker, Worker } from 'tesseract.js';
+import { I18nService } from '../i18n/i18n.service';
+
+@Injectable()
+export class OcrService {
+  private readonly logger = new Logger(OcrService.name);
+
+  constructor(private readonly i18n: I18nService) {}
+
+  async extractTextFromImage(imageBuffer: Buffer): Promise<string> {
+    this.logger.log(
+      `Starting OCR extraction from image (${imageBuffer.length} bytes)...`,
+    );
+
+    // Create worker for this request to ensure stability
+    let worker: any = null;
+    try {
+      worker = await createWorker('chi_sim+eng+jpn');
+
+      const {
+        data: { text },
+      } = await worker.recognize(imageBuffer);
+      this.logger.log(
+        `OCR extraction completed. ${text.length} characters extracted.`,
+      );
+
+      if (text.length === 0) {
+        this.logger.warn('OCR returned empty text.');
+      }
+
+      await worker.terminate();
+      return text.trim();
+    } catch (error) {
+      this.logger.error(`OCR text extraction failed: ${error.message}`);
+      if (worker) {
+        try {
+          await worker.terminate();
+        } catch (e) {}
+      }
+      throw new Error(
+        this.i18n.formatMessage('ocrFailed', { message: error.message }),
+      );
+    }
+  }
+
+  async extractTextWithConfidence(imageBuffer: Buffer): Promise<{
+    text: string;
+    confidence: number;
+  }> {
+    this.logger.log(
+      `Starting OCR extraction with confidence (${imageBuffer.length} bytes)...`,
+    );
+
+    let worker: any = null;
+    try {
+      worker = await createWorker('chi_sim+eng+jpn');
+      const { data } = await worker.recognize(imageBuffer);
+      this.logger.log(
+        `OCR extraction completed. Confidence: ${data.confidence}%`,
+      );
+
+      await worker.terminate();
+      return {
+        text: data.text.trim(),
+        confidence: data.confidence,
+      };
+    } catch (error) {
+      this.logger.error(`OCR text extraction failed: ${error.message}`);
+      if (worker) {
+        try {
+          await worker.terminate();
+        } catch (e) {}
+      }
+      throw new Error(
+        this.i18n.formatMessage('ocrFailed', { message: error.message }),
+      );
+    }
+  }
+}