fix(provider): 模型测试按 Key 模型权限过滤

测试模型前检查 provider key 的 allowed_models：
- 空权限视为允许所有模型
- 非空权限需匹配请求模型或映射后的实际模型
- 不匹配的 key 标记为跳过，避免发起测试请求

同时补充相关单测和前端跳过原因文案。

frontend/src/features/providers/components/provider-tabs/__tests__/model-test-request.spec.ts

@@ -372,6 +372,11 @@ describe('isModelTestableEndpoint', () => {
 })
 
 describe('formatModelTestDiagnostic', () => {
+  it('maps model permission skips to an actionable label', () => {
+    expect(formatModelTestDiagnostic('key_model_not_allowed'))
+      .toBe('Key 未允许当前模型，已跳过')
+  })
+
   it('maps pool account blocked scheduler code to an actionable label', () => {
     expect(formatModelTestDiagnostic('pool_account_blocked')).toBe('账号已失效，需重新授权')
   })

frontend/src/features/providers/components/provider-tabs/model-test-capabilities.ts

@@ -41,6 +41,7 @@ const MODEL_TEST_BEARER_INHERITS_PROVIDER_FORMATS = new Set([
 ])
 
 const MODEL_TEST_DIAGNOSTIC_LABELS: Record<string, string> = {
+  key_model_not_allowed: 'Key 未允许当前模型，已跳过',
   pool_account_blocked: '账号已失效，需重新授权',
 }