feat(api): add v2 phase one skeleton

backend/src/test/java/com/yoyuzh/api/v2/ApiV2ExceptionHandlerTest.java

@@ -0,0 +1,36 @@
+package com.yoyuzh.api.v2;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ApiV2ExceptionHandlerTest {
+
+    private final ApiV2ExceptionHandler handler = new ApiV2ExceptionHandler();
+
+    @Test
+    void shouldMapV2BusinessErrorsToV2ResponseEnvelope() {
+        ResponseEntity<ApiV2Response<Void>> response = handler.handleApiV2Exception(
+                new ApiV2Exception(ApiV2ErrorCode.FILE_NOT_FOUND, "文件不存在")
+        );
+
+        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.NOT_FOUND);
+        assertThat(response.getBody()).isNotNull();
+        assertThat(response.getBody().code()).isEqualTo(ApiV2ErrorCode.FILE_NOT_FOUND.getCode());
+        assertThat(response.getBody().msg()).isEqualTo("文件不存在");
+        assertThat(response.getBody().data()).isNull();
+    }
+
+    @Test
+    void shouldKeepUnknownV2ErrorsInsideTheV2ErrorCodeRange() {
+        ResponseEntity<ApiV2Response<Void>> response = handler.handleUnknownException(new RuntimeException("boom"));
+
+        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.INTERNAL_SERVER_ERROR);
+        assertThat(response.getBody()).isNotNull();
+        assertThat(response.getBody().code()).isEqualTo(ApiV2ErrorCode.INTERNAL_ERROR.getCode());
+        assertThat(response.getBody().msg()).isEqualTo("服务器内部错误");
+        assertThat(response.getBody().data()).isNull();
+    }
+}

backend/src/test/java/com/yoyuzh/api/v2/site/SiteV2ControllerTest.java

@@ -0,0 +1,30 @@
+package com.yoyuzh.api.v2.site;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+class SiteV2ControllerTest {
+
+    private MockMvc mockMvc;
+
+    @BeforeEach
+    void setUp() {
+        mockMvc = MockMvcBuilders.standaloneSetup(new SiteV2Controller()).build();
+    }
+
+    @Test
+    void shouldExposeV2PingWithV2ResponseEnvelope() throws Exception {
+        mockMvc.perform(get("/api/v2/site/ping"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.code").value(0))
+                .andExpect(jsonPath("$.msg").value("success"))
+                .andExpect(jsonPath("$.data.status").value("ok"))
+                .andExpect(jsonPath("$.data.apiVersion").value("v2"));
+    }
+}