feat: add useStickerWall hook for shared fetch/render logic

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/hooks/useStickerWall.js

@@ -0,0 +1,76 @@
+import { useState, useEffect, useRef, useCallback } from 'react';
+import api from '../api/axios';
+
+export function useStickerWall(sessionId) {
+  const [imageUrl, setImageUrl] = useState(null);
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState(false);
+  const urlRef = useRef(null);
+
+  const revokeUrl = useCallback(() => {
+    if (urlRef.current) {
+      URL.revokeObjectURL(urlRef.current);
+      urlRef.current = null;
+    }
+  }, []);
+
+  const setBlobUrl = useCallback((blob) => {
+    revokeUrl();
+    const url = URL.createObjectURL(blob);
+    urlRef.current = url;
+    setImageUrl(url);
+  }, [revokeUrl]);
+
+  const fetchWall = useCallback(async (id) => {
+    setLoading(true);
+    setError(false);
+    try {
+      const res = await api.get(`/stickerwalls/${id}`, { responseType: 'blob' });
+      setBlobUrl(res.data);
+    } catch (err) {
+      if (err.response?.status === 404) {
+        try {
+          const renderRes = await api.post(`/stickerwalls/${id}/render`, null, { responseType: 'blob' });
+          setBlobUrl(renderRes.data);
+        } catch (renderErr) {
+          revokeUrl();
+          setImageUrl(null);
+          setError(true);
+        }
+      } else {
+        revokeUrl();
+        setImageUrl(null);
+        setError(true);
+      }
+    } finally {
+      setLoading(false);
+    }
+  }, [setBlobUrl, revokeUrl]);
+
+  const refresh = useCallback(async () => {
+    if (!sessionId) return;
+    setLoading(true);
+    setError(false);
+    try {
+      const res = await api.post(`/stickerwalls/${sessionId}/render`, null, { responseType: 'blob' });
+      setBlobUrl(res.data);
+    } catch {
+      setError(true);
+    } finally {
+      setLoading(false);
+    }
+  }, [sessionId, setBlobUrl]);
+
+  useEffect(() => {
+    if (sessionId) {
+      fetchWall(sessionId);
+    } else {
+      revokeUrl();
+      setImageUrl(null);
+      setError(false);
+    }
+    return revokeUrl;
+  }, [sessionId, fetchWall, revokeUrl]);
+
+  return { imageUrl, loading, error, refresh };
+}