feat(gif): favourites and category shortcuts

Favourites are stored server-side per user, so one made on the phone is there
on the desktop — the point of favouriting. The whole result is stored rather
than an id: the provider offers no lookup by id, so an id-only favourite could
not be rendered without re-finding it through search.

Category chips translate their label but not their query, which goes to a
provider that indexes in English.

The star sits beside the tile button rather than inside it: a button within a
button is invalid and swallows the click. Toggling is optimistic and reverts
on failure, and favourites skip both the loading skeleton and the infinite
scroll, which belong to provider-backed browsing only.

Server caps favourites per user and rejects non-http(s) URLs, which become
<img src> in everyone's picker.

packages/web/src/components/chat/GifPicker.tsx

@@ -1,6 +1,21 @@
 import React, { useState, useEffect, useRef, useCallback } from 'react';
 import { api } from '../../api/client';
 import type { GifResult } from '@backspace/shared';
+import { useT, type TranslationKey } from '../../i18n';
+
+/**
+ * Category shortcuts. The label is translated but the query is not: it is sent
+ * to the provider, which indexes in English — a translated query would return
+ * nothing.
+ */
+const CATEGORIES: { key: TranslationKey; query: string }[] = [
+  { key: 'gif.category.hello', query: 'hello' },
+  { key: 'gif.category.lol', query: 'lol' },
+  { key: 'gif.category.love', query: 'love' },
+  { key: 'gif.category.birthday', query: 'happy birthday' },
+  { key: 'gif.category.dance', query: 'dance' },
+  { key: 'gif.category.facepalm', query: 'facepalm' },
+];
 
 interface GifPickerProps {
   onGifSelect: (url: string) => void;
@@ -12,6 +27,10 @@ interface GifPickerProps {
 }
 
 export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
+  const t = useT();
+  const [showFavorites, setShowFavorites] = useState(false);
+  const [favorites, setFavorites] = useState<GifResult[]>([]);
+  const [favoriteIds, setFavoriteIds] = useState<Set<string>>(new Set());
   const [query, setQuery] = useState('');
   const [debouncedQuery, setDebouncedQuery] = useState('');
   const [results, setResults] = useState<GifResult[]>([]);
@@ -21,6 +40,46 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
   const scrollRef = useRef<HTMLDivElement>(null);
   const debounceRef = useRef<ReturnType<typeof setTimeout>>();
 
+  // Favourites load once and are kept in memory: the picker is opened and
+  // closed constantly, and re-fetching on every open would be visible.
+  useEffect(() => {
+    let cancelled = false;
+    api.gif.favorites()
+      .then(({ results }) => {
+        if (cancelled) return;
+        setFavorites(results);
+        setFavoriteIds(new Set(results.map((g) => g.id)));
+      })
+      .catch(() => { /* favourites are an enhancement; browsing still works */ });
+    return () => { cancelled = true; };
+  }, []);
+
+  const toggleFavorite = async (gif: GifResult, e: React.MouseEvent) => {
+    // The tile behind this button inserts the GIF into the message.
+    e.stopPropagation();
+    const isFavorite = favoriteIds.has(gif.id);
+
+    // Optimistic: the star must feel instant. Reverted below if the call fails.
+    setFavoriteIds((prev) => {
+      const next = new Set(prev);
+      if (isFavorite) next.delete(gif.id); else next.add(gif.id);
+      return next;
+    });
+    setFavorites((prev) => (isFavorite ? prev.filter((g) => g.id !== gif.id) : [gif, ...prev]));
+
+    try {
+      if (isFavorite) await api.gif.removeFavorite(gif.id);
+      else await api.gif.addFavorite(gif);
+    } catch {
+      setFavoriteIds((prev) => {
+        const next = new Set(prev);
+        if (isFavorite) next.add(gif.id); else next.delete(gif.id);
+        return next;
+      });
+      setFavorites((prev) => (isFavorite ? [gif, ...prev] : prev.filter((g) => g.id !== gif.id)));
+    }
+  };
+
   // Debounce search query
   useEffect(() => {
     if (debounceRef.current) clearTimeout(debounceRef.current);
@@ -60,6 +119,8 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
   // Infinite scroll
   const handleScroll = useCallback(() => {
     const el = scrollRef.current;
+    // Favourites are a complete local list — nothing to page through.
+    if (showFavorites) return;
     if (!el || loadingMore || !nextPos) return;
     if (el.scrollTop + el.clientHeight >= el.scrollHeight - 100) {
       setLoadingMore(true);
@@ -76,13 +137,16 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
       };
       fetchMore();
     }
-  }, [loadingMore, nextPos, debouncedQuery]);
+  }, [loadingMore, nextPos, debouncedQuery, showFavorites]);
 
   // Prevent keyboard events from bubbling
   const handleKeyDown = (e: React.KeyboardEvent) => {
     e.stopPropagation();
   };
 
+  // Favourites are a local list; browsing results come from the provider.
+  const shown = showFavorites ? favorites : results;
+
   // Mobile: fill parent (sheet sets width + max-height). Desktop: fixed dims
   // matching the legacy popover footprint.
   const rootClass = mobile
@@ -97,7 +161,7 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
           type="text"
           value={query}
           onChange={(e) => setQuery(e.target.value)}
-          placeholder="Search GIFs"
+          placeholder={t('gif.search')}
           className="input-search w-full"
           // Auto-focus only on desktop. On mobile this would force the OS
           // keyboard up the moment the sheet opens, hiding most of the grid.
@@ -105,13 +169,41 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
         />
       </div>
 
+      {/* Category shortcuts */}
+      <div className="flex gap-1.5 px-3 pb-2 overflow-x-auto no-scrollbar shrink-0">
+        <button
+          type="button"
+          onClick={() => setShowFavorites((v) => !v)}
+          className={`px-2.5 py-1 rounded-full text-[12px] font-medium whitespace-nowrap transition-colors flex items-center gap-1 ${
+            showFavorites
+              ? 'bg-accent-primary text-white'
+              : 'bg-surface-elevated text-txt-secondary hover:text-txt-primary'
+          }`}
+        >
+          <svg width="11" height="11" viewBox="0 0 24 24" fill="currentColor" aria-hidden="true">
+            <path d="m12 17.27 6.18 3.73-1.64-7.03L22 9.24l-7.19-.61L12 2 9.19 8.63 2 9.24l5.46 4.73L5.82 21z" />
+          </svg>
+          {t('gif.tab.favorites')}
+        </button>
+        {CATEGORIES.map((category) => (
+          <button
+            key={category.query}
+            type="button"
+            onClick={() => { setShowFavorites(false); setQuery(category.query); }}
+            className="px-2.5 py-1 rounded-full text-[12px] font-medium whitespace-nowrap bg-surface-elevated text-txt-secondary hover:text-txt-primary transition-colors"
+          >
+            {t(category.key)}
+          </button>
+        ))}
+      </div>
+
       {/* Results grid */}
       <div
         ref={scrollRef}
         className="flex-1 overflow-y-auto scrollbar-thin px-2 pb-1"
         onScroll={handleScroll}
       >
-        {loading ? (
+        {loading && !showFavorites ? (
           <div className="grid grid-cols-2 gap-1.5 p-1">
             {Array.from({ length: 6 }).map((_, i) => (
               <div
@@ -121,29 +213,52 @@ export function GifPicker({ onGifSelect, mobile = false }: GifPickerProps) {
               />
             ))}
           </div>
-        ) : results.length === 0 ? (
-          <div className="flex items-center justify-center h-full text-txt-tertiary text-sm">
-            {debouncedQuery.trim() ? 'No GIFs found' : 'No trending GIFs'}
+        ) : shown.length === 0 ? (
+          <div className="flex items-center justify-center h-full text-txt-tertiary text-sm text-center px-4">
+            {showFavorites
+              ? t('gif.empty.favorites')
+              : debouncedQuery.trim()
+                ? t('gif.empty.search')
+                : t('gif.empty.trending')}
           </div>
         ) : (
           <div className="columns-2 gap-1.5 p-1">
-            {results.map((gif) => (
-              <button
-                key={gif.id}
-                onClick={() => onGifSelect(gif.url)}
-                className="w-full mb-1.5 rounded-lg overflow-hidden hover:ring-2 hover:ring-accent-primary transition-all break-inside-avoid"
-              >
-                <img
-                  src={gif.previewUrl}
-                  alt={gif.title}
-                  className="w-full object-cover rounded-lg"
-                  loading="lazy"
-                  style={{
-                    aspectRatio: gif.width && gif.height ? `${gif.width}/${gif.height}` : undefined,
-                  }}
-                />
-              </button>
-            ))}
+            {shown.map((gif) => {
+              const isFavorite = favoriteIds.has(gif.id);
+              return (
+                // The star cannot live inside the tile button — a button inside
+                // a button is invalid and swallows the click. Siblings instead.
+                <div key={gif.id} className="relative group w-full mb-1.5 break-inside-avoid">
+                  <button
+                    onClick={() => onGifSelect(gif.url)}
+                    className="w-full rounded-lg overflow-hidden hover:ring-2 hover:ring-accent-primary transition-all block"
+                  >
+                    <img
+                      src={gif.previewUrl}
+                      alt={gif.title}
+                      className="w-full object-cover rounded-lg"
+                      loading="lazy"
+                      style={{
+                        aspectRatio: gif.width && gif.height ? `${gif.width}/${gif.height}` : undefined,
+                      }}
+                    />
+                  </button>
+                  <button
+                    type="button"
+                    onClick={(e) => void toggleFavorite(gif, e)}
+                    title={isFavorite ? t('gif.favorite.remove') : t('gif.favorite.add')}
+                    aria-label={isFavorite ? t('gif.favorite.remove') : t('gif.favorite.add')}
+                    className={`absolute top-1.5 right-1.5 w-7 h-7 rounded-full flex items-center justify-center bg-black/55 backdrop-blur-sm transition-opacity ${
+                      isFavorite ? 'opacity-100 text-accent-amber' : 'opacity-0 group-hover:opacity-100 focus:opacity-100 text-white'
+                    }`}
+                  >
+                    <svg width="14" height="14" viewBox="0 0 24 24" fill={isFavorite ? 'currentColor' : 'none'} stroke="currentColor" strokeWidth="2">
+                      <path d="m12 17.27 6.18 3.73-1.64-7.03L22 9.24l-7.19-.61L12 2 9.19 8.63 2 9.24l5.46 4.73L5.82 21z" />
+                    </svg>
+                  </button>
+                </div>
+              );
+            })}
           </div>
         )}
         {loadingMore && (