feat(server): CORS 中间件(Web 用户中心跨域调 /v1/*)

usercenter(app.yanmeiai.com,浏览器)跨域调控制面 API 会被浏览器拦(无 CORS 头)。
加白名单 CORS 中间件(CORS_ORIGINS,缺省 app.yanmeiai.com + pages.dev),应答 OPTIONS
预检。原生端非浏览器不受影响。Bearer 认证故不需 Allow-Credentials。含 3 项测试。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

server/cmd/server/main.go

@@ -123,6 +123,8 @@ func main() {
 	r.Use(chimw.Logger)
 	r.Use(chimw.Recoverer)
 	r.Use(apierr.Middleware)
+	// CORS:Web 用户中心(app.yanmeiai.com)跨域调 /v1/*;原生端不受影响。
+	r.Use(httpapi.NewCORS())
 
 	r.Get("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")

server/internal/httpapi/cors.go

@@ -0,0 +1,47 @@
+package httpapi
+
+import (
+	"net/http"
+	"os"
+	"strings"
+)
+
+// NewCORS 返回一个 CORS 中间件:为白名单 Origin(精确匹配)补 CORS 响应头,并直接
+// 应答 OPTIONS 预检。Web 用户中心(app.yanmeiai.com,浏览器)跨域调用 /v1/*,浏览器
+// 会先发预检、并校验 Access-Control-Allow-Origin;原生移动/桌面客户端不是浏览器、
+// 不受 CORS 约束,故此前无需 CORS。
+//
+// Origin 白名单来自 CORS_ORIGINS(逗号分隔),缺省含 usercenter 的正式域与 pages.dev。
+// 认证走 Authorization: Bearer(非 cookie),所以不需要 Allow-Credentials。
+func NewCORS() func(http.Handler) http.Handler {
+	raw := os.Getenv("CORS_ORIGINS")
+	if raw == "" {
+		raw = "https://app.yanmeiai.com,https://pangolin-usercenter.pages.dev"
+	}
+	allowed := map[string]bool{}
+	for _, o := range strings.Split(raw, ",") {
+		o = strings.TrimSpace(o)
+		if o != "" {
+			allowed[o] = true
+		}
+	}
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			origin := r.Header.Get("Origin")
+			if origin != "" && allowed[origin] {
+				h := w.Header()
+				h.Set("Access-Control-Allow-Origin", origin)
+				h.Add("Vary", "Origin")
+				h.Set("Access-Control-Allow-Methods", "GET, POST, PUT, PATCH, DELETE, OPTIONS")
+				h.Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
+				h.Set("Access-Control-Max-Age", "600")
+			}
+			// 预检请求直接 204(不落到业务路由,避免 /v1/... 的 OPTIONS 404)。
+			if r.Method == http.MethodOptions {
+				w.WriteHeader(http.StatusNoContent)
+				return
+			}
+			next.ServeHTTP(w, r)
+		})
+	}
+}

server/internal/httpapi/cors_test.go

@@ -0,0 +1,47 @@
+package httpapi
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestCORS(t *testing.T) {
+	t.Setenv("CORS_ORIGINS", "https://app.yanmeiai.com")
+	mw := NewCORS()
+	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(200) })
+	h := mw(next)
+
+	// 允许的 Origin:补 Allow-Origin,普通请求继续。
+	r := httptest.NewRequest("POST", "/v1/auth/login", nil)
+	r.Header.Set("Origin", "https://app.yanmeiai.com")
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, r)
+	if got := w.Header().Get("Access-Control-Allow-Origin"); got != "https://app.yanmeiai.com" {
+		t.Fatalf("allowed origin: want header, got %q", got)
+	}
+	if w.Code != 200 {
+		t.Fatalf("non-preflight should reach next, got %d", w.Code)
+	}
+
+	// OPTIONS 预检:204,不落到业务。
+	r = httptest.NewRequest("OPTIONS", "/v1/auth/login", nil)
+	r.Header.Set("Origin", "https://app.yanmeiai.com")
+	w = httptest.NewRecorder()
+	h.ServeHTTP(w, r)
+	if w.Code != http.StatusNoContent {
+		t.Fatalf("preflight: want 204, got %d", w.Code)
+	}
+	if w.Header().Get("Access-Control-Allow-Methods") == "" {
+		t.Fatalf("preflight missing Allow-Methods")
+	}
+
+	// 未白名单 Origin:不补 Allow-Origin。
+	r = httptest.NewRequest("POST", "/v1/auth/login", nil)
+	r.Header.Set("Origin", "https://evil.example.com")
+	w = httptest.NewRecorder()
+	h.ServeHTTP(w, r)
+	if got := w.Header().Get("Access-Control-Allow-Origin"); got != "" {
+		t.Fatalf("disallowed origin should get no header, got %q", got)
+	}
+}