refactor: 优化测试框架配置

- 删除冗余的config/test/jest.config.js
- 将jest.config.js从符号链接改为独立配置文件
- 提升测试覆盖率阈值:
  - branches: 41% -> 50%
  - functions: 47% -> 55%
  - lines: 52% -> 60%
  - statements: 51% -> 60%
- 添加Jest缓存目录配置优化CI性能

config/test/jest.config.js

@@ -1,41 +0,0 @@
-module.exports = {
-  preset: 'ts-jest',
-  testEnvironment: 'jsdom',
-  roots: ['<rootDir>/src'],
-  testMatch: ['**/__tests__/**/*.test.{ts,tsx}', '**/*.test.{ts,tsx}'],
-  collectCoverageFrom: [
-    'src/**/*.{ts,tsx}',
-    '!src/**/*.d.ts',
-    '!src/**/*.stories.{ts,tsx}',
-    '!src/**/__tests__/**',
-  ],
-  coverageThreshold: {
-    global: {
-      branches: 41,
-      functions: 47,
-      lines: 52,
-      statements: 51,
-    },
-  },
-  coverageReporters: ['text', 'lcov', 'html', 'json'],
-  coverageDirectory: 'coverage',
-  moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
-  moduleNameMapper: {
-    '^@/(.*)$': '<rootDir>/src/$1',
-  },
-  transform: {
-    '^.+\\.(ts|tsx)$': [
-      'ts-jest',
-      {
-        tsconfig: 'tsconfig.test.json',
-      },
-    ],
-  },
-  transformIgnorePatterns: [
-    'node_modules/(?!(nanoid|next-auth|@auth)/)',
-  ],
-  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
-  testTimeout: 10000,
-  verbose: true,
-  maxWorkers: '50%',
-};