feat: E2E 测试集成真实后端

- Playwright 双 webServer 模式自动启动 Go 后端 + Vite 前端
- 后端使用临时 SQLite 数据库隔离，固定端口 19026
- vite.config.ts proxy target 动态读取环境变量
- 新增 sql.js 依赖用于 SQLite 统计数据 seed
- 新增 e2e/fixtures.ts 共享工具模块（API seed + SQLite seed）
- 拆分测试文件 5→7（providers/models/stats/navigation/validation）
- 删除旧文件 crud.spec.ts/sidebar.spec.ts/stats-cards.spec.ts
- E2E 测试尚有部分用例需调试修复

frontend/playwright.config.ts

@@ -1,8 +1,27 @@
 import { defineConfig, devices } from '@playwright/test'
+import fs from 'node:fs'
+import os from 'node:os'
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const __filename = fileURLToPath(import.meta.url)
+const __dirname = path.dirname(__filename)
+
+const E2E_PORT = 19026
+const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'nex-e2e-'))
+const dbPath = path.join(tempDir, 'test.db')
+const logPath = path.join(tempDir, 'log')
+
+fs.mkdirSync(logPath, { recursive: true })
+
+process.env.NEX_BACKEND_PORT = String(E2E_PORT)
+process.env.NEX_E2E_TEMP_DIR = tempDir
+
+const backendDir = path.resolve(__dirname, '..', 'backend')
 
 export default defineConfig({
   testDir: './e2e',
-  fullyParallel: true,
+  fullyParallel: false,
   forbidOnly: !!process.env.CI,
   retries: process.env.CI ? 2 : 0,
   workers: process.env.CI ? 1 : undefined,
@@ -17,9 +36,20 @@ export default defineConfig({
       use: { ...devices['Desktop Chrome'] },
     },
   ],
-  webServer: {
-    command: 'bun run dev',
-    url: 'http://localhost:5173',
-    reuseExistingServer: !process.env.CI,
-  },
+  globalSetup: './e2e/global-setup.ts',
+  globalTeardown: './e2e/global-teardown.ts',
+  webServer: [
+    {
+      command: `go run cmd/server/main.go --server-port ${E2E_PORT} --database-path "${dbPath}" --log-path "${logPath}" --log-level warn`,
+      url: `http://localhost:${E2E_PORT}/health`,
+      timeout: 60_000,
+      reuseExistingServer: false,
+      cwd: backendDir,
+    },
+    {
+      command: 'bun run dev',
+      url: 'http://localhost:5173',
+      reuseExistingServer: false,
+    },
+  ],
 })