feat: 媒体库 blob 去重存储与品牌/注册等前端调整

新增：
- blob_store 二进制去重存储 + blob_dedup 测试

其它：
- 后端 settings/auth/media_library/upload/operations 服务与 handler 调整
- 前端品牌（BrandLockup/BrandCropModal/BrandSeoPanel）、注册、媒体库、分析详情页、Header/SiteChrome 等更新

frontend/app/register/RegisterClient.tsx

@@ -1,6 +1,6 @@
 "use client";
 
-import { useState, useEffect } from "react";
+import { useState, useEffect, useRef } from "react";
 import { useRouter } from "next/navigation";
 import Link from "next/link";
 import { UserPlus } from "lucide-react";
@@ -44,8 +44,33 @@ export default function RegisterClient({
   const [notice, setNotice] = useState(registerNotice);
   const [sending, setSending] = useState(false);
   const [sentMessage, setSentMessage] = useState("");
+  // 重发倒计时（秒）；>0 期间按钮锁定不可点
+  const [countdown, setCountdown] = useState(0);
+  const countdownTimer = useRef<ReturnType<typeof setInterval> | null>(null);
   const verifyEmail = initialVerifyEmail;
 
+  // 卸载时清理倒计时，避免泄漏
+  useEffect(() => {
+    return () => {
+      if (countdownTimer.current) clearInterval(countdownTimer.current);
+    };
+  }, []);
+
+  const startCountdown = () => {
+    if (countdownTimer.current) clearInterval(countdownTimer.current);
+    setCountdown(60);
+    countdownTimer.current = setInterval(() => {
+      setCountdown((c) => {
+        if (c <= 1) {
+          if (countdownTimer.current) clearInterval(countdownTimer.current);
+          countdownTimer.current = null;
+          return 0;
+        }
+        return c - 1;
+      });
+    }, 1000);
+  };
+
   // 已登录用户不必再注册，直接回首页
   useEffect(() => {
     if (!hasAuthCookieHint()) return;
@@ -166,8 +191,9 @@ export default function RegisterClient({
               <button
                 type="button"
                 className="btn btn-line shrink-0"
-                disabled={sending || !email}
+                disabled={sending || countdown > 0 || !email}
                 onClick={async () => {
+                  // 点击即锁定，防止重复发送
                   setSending(true);
                   setError("");
                   try {
@@ -176,6 +202,7 @@ export default function RegisterClient({
                       purpose: "register",
                     });
                     setSentMessage(r.message);
+                    startCountdown();
                   } catch (err) {
                     setError((err as Error).message);
                   } finally {
@@ -183,7 +210,11 @@ export default function RegisterClient({
                   }
                 }}
               >
-                {sending ? "正在排队…" : "发送验证码"}
+                {sending
+                  ? "正在排队…"
+                  : countdown > 0
+                    ? `${countdown}s 后可重发`
+                    : "发送验证码"}
               </button>
             </div>
             {sentMessage && (