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/api/api.controller.ts

@@ -0,0 +1,72 @@
+import {
+  Body,
+  Controller,
+  Get,
+  HttpCode,
+  HttpStatus,
+  Post,
+  Request,
+  UseGuards,
+} from '@nestjs/common';
+import { ApiService } from './api.service';
+import { CombinedAuthGuard } from '../auth/combined-auth.guard';
+import { ModelConfigService } from '../model-config/model-config.service';
+import { I18nService } from '../i18n/i18n.service';
+
+class ChatDto {
+  prompt: string;
+}
+
+@Controller()
+export class ApiController {
+  constructor(
+    private readonly apiService: ApiService,
+    private readonly modelConfigService: ModelConfigService,
+    private readonly i18nService: I18nService,
+  ) {}
+
+  @Get('health')
+  healthCheck() {
+    return this.apiService.healthCheck();
+  }
+
+  @Post('chat')
+  @UseGuards(CombinedAuthGuard)
+  @HttpCode(HttpStatus.OK)
+  async chat(@Request() req, @Body() chatDto: ChatDto) {
+    const { prompt } = chatDto;
+    if (!prompt) {
+      throw new Error(this.i18nService.getMessage('promptRequired'));
+    }
+
+    try {
+      // ユーザーの LLM モデル設定を取得
+      const models = await this.modelConfigService.findAll();
+      const llmModel = models.find((m) => m.type === 'llm');
+      if (!llmModel) {
+        throw new Error(this.i18nService.getMessage('addLLMConfig'));
+      }
+
+      // API key is optional - allows local models
+
+      const modelConfigForService = {
+        id: llmModel.id,
+        name: llmModel.name,
+        modelId: llmModel.modelId,
+        baseUrl: llmModel.baseUrl,
+        apiKey: llmModel.apiKey,
+        type: llmModel.type as any,
+      };
+
+      const response = await this.apiService.getChatCompletion(
+        prompt,
+        modelConfigForService,
+      );
+      return { response };
+    } catch (error) {
+      throw new Error(
+        error.message || this.i18nService.getMessage('internalServerError'),
+      );
+    }
+  }
+}