feat: 添加分享结果卡片功能，形成用户增长闭环

- 新增 ShareCardModal 组件，支持餐厅匹配和盲盒契约两种分享卡片
- 卡片包含品牌标识、匹配结果、餐厅/想法详情、二维码
- 使用 html-to-image 生成高清 PNG，支持保存图片和 Web Share API 分享
- 餐厅图片通过 canvas 转 data URL 处理跨域
- 集成到 MatchResult（极速救场）和 BlindBox reveal（周末契约）

src/app/blindbox/[code]/page.tsx

@@ -17,6 +17,7 @@ import {
 } from "lucide-react";
 import confetti from "canvas-confetti";
 import { getCachedProfile, isRegistered } from "@/lib/userId";
+import ShareCardModal from "@/components/ShareCardModal";
 import type { UserProfile } from "@/types";
 
 interface RoomInfo {
@@ -57,6 +58,7 @@ export default function BlindboxRoomPage() {
   const [submitFlash, setSubmitFlash] = useState(false);
   const [error, setError] = useState("");
   const [showInvite, setShowInvite] = useState(false);
+  const [showShareCard, setShowShareCard] = useState(false);
   const [toast, setToast] = useState("");
 
   const boxControls = useAnimation();
@@ -522,13 +524,23 @@ export default function BlindboxRoomPage() {
                   </div>
                 </div>
 
-                <motion.button
-                  onClick={() => { setPhase("pool"); setRevealedIdea(null); }}
-                  className="flex h-10 items-center gap-2 rounded-full bg-surface px-5 text-xs font-semibold text-muted ring-1 ring-border transition-colors hover:bg-elevated"
-                  whileTap={{ scale: 0.96 }}
-                >
-                  继续投入想法
-                </motion.button>
+                <div className="flex items-center gap-3">
+                  <motion.button
+                    onClick={() => setShowShareCard(true)}
+                    className="flex h-10 items-center gap-2 rounded-full bg-purple-600 px-5 text-xs font-bold text-white shadow-lg shadow-purple-900/30 transition-colors hover:bg-purple-500"
+                    whileTap={{ scale: 0.96 }}
+                  >
+                    <Share2 size={14} />
+                    分享契约
+                  </motion.button>
+                  <motion.button
+                    onClick={() => { setPhase("pool"); setRevealedIdea(null); setShowShareCard(false); }}
+                    className="flex h-10 items-center gap-2 rounded-full bg-surface px-5 text-xs font-semibold text-muted ring-1 ring-border transition-colors hover:bg-elevated"
+                    whileTap={{ scale: 0.96 }}
+                  >
+                    继续投入想法
+                  </motion.button>
+                </div>
               </motion.div>
             )}
           </AnimatePresence>
@@ -590,6 +602,24 @@ export default function BlindboxRoomPage() {
         </>
       )}
 
+      {revealedIdea && room && (
+        <ShareCardModal
+          open={showShareCard}
+          onClose={() => setShowShareCard(false)}
+          data={{
+            type: "blindbox",
+            idea: revealedIdea.content,
+            submitter: revealedIdea.user ?? undefined,
+            drawer: revealedIdea.drawnBy ?? undefined,
+            roomName: room.name,
+          }}
+          onToast={(msg) => {
+            setToast(msg);
+            setTimeout(() => setToast(""), 2200);
+          }}
+        />
+      )}
+
       {/* Toast */}
       <AnimatePresence>
         {toast && (