feat: 集成 KieAI 服务，移除 models-integration 子项目

- 添加 Gemini 2.5 Flash 对话接口（流式+非流式）
- 添加 NanoBanana 图像生成/编辑接口
- 添加 Sora2 视频生成接口（文生视频、图生视频、去水印）
- 移除 models-integration 子项目（功能已迁移至主后端）
- 新增测试文档和 Playwright E2E 配置
- 更新前端页面和 API 接口
- 更新后端配置和日志处理

playwright.config.ts

@@ -0,0 +1,42 @@
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './tests/e2e',
+  timeout: 30_000,
+  expect: { timeout: 8_000 },
+  fullyParallel: false,
+  retries: 1,
+  reporter: [
+    ['html', { outputFolder: 'tests/e2e/reports', open: 'never' }],
+    ['list'],
+  ],
+  outputDir: 'tests/e2e/test-results',
+
+  use: {
+    baseURL: 'http://localhost:8080',
+    // Mobile viewport simulating iPhone SE
+    viewport: { width: 375, height: 667 },
+    userAgent:
+      'Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.0 Mobile/15E148 Safari/604.1',
+    screenshot: 'only-on-failure',
+    video: 'retain-on-failure',
+    trace: 'retain-on-failure',
+    // Ignore HTTPS errors from local dev server
+    ignoreHTTPSErrors: true,
+  },
+
+  projects: [
+    {
+      name: 'mobile-chrome',
+      use: {
+        browserName: 'chromium',
+        viewport: { width: 375, height: 667 },
+        userAgent:
+          'Mozilla/5.0 (Linux; Android 13; Pixel 7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Mobile Safari/537.36',
+        deviceScaleFactor: 2,
+        isMobile: true,
+        hasTouch: true,
+      },
+    },
+  ],
+});