fix(settings): say when GIF search isn't set up instead of a dead switch

The GIF button needs a Giphy key in the client config. Without one (the
desktop app until now), switching "GIF Picker" on did nothing and nothing
said why. With no key the tile now explains it and the switch is disabled;
with a key it is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/settings/general/General.tsx

@@ -49,6 +49,7 @@ import {
   Edge,
 } from '@atlaskit/pragmatic-drag-and-drop-hitbox/closest-edge';
 import { useAtom } from 'jotai';
+import { useClientConfig } from '../../../hooks/useClientConfig';
 import { HexColorPickerPopOut } from '../../../components/HexColorPickerPopOut';
 import { BgSwatch as BgSwatchStyle } from './BgSwatch.css';
 import { Page, PageContent, PageHeader } from '../../../components/page';
@@ -2581,6 +2582,8 @@ function Messages() {
   );
   const [autoTranslate, setAutoTranslate] = useSetting(settingsAtom, 'autoTranslate');
   const [gifPickerEnabled, setGifPickerEnabled] = useSetting(settingsAtom, 'gifPickerEnabled');
+  // No Giphy key in this build's config: the switch can't show a GIF button.
+  const gifAvailable = !!useClientConfig().gifApiKey;
   const translationSupported = chromeTranslationEngine.isSupported();
   const selectedTargetLang = isSupportedTargetLang(translateTargetLang)
     ? normalizeLang(translateTargetLang)
@@ -2686,9 +2689,18 @@ function Messages() {
       <SequenceCard className={SequenceCardStyle} variant="SurfaceVariant" direction="Column">
         <SettingTile
           title="GIF Picker"
-          description="Every search term (and your IP address) is sent directly to Giphy, not through your homeserver. Off by default."
+          description={
+            gifAvailable
+              ? 'Every search term (and your IP address) is sent directly to Giphy, not through your homeserver. Off by default.'
+              : "GIF search isn't set up for this version of the app (no Giphy key in its configuration), so there is no GIF button even when this is on."
+          }
           after={
-            <Switch variant="Primary" value={gifPickerEnabled} onChange={setGifPickerEnabled} />
+            <Switch
+              variant="Primary"
+              value={gifPickerEnabled && gifAvailable}
+              onChange={setGifPickerEnabled}
+              disabled={!gifAvailable}
+            />
           }
         />
       </SequenceCard>