i18n: localize hardcoded UI strings across 10 components

Wraps the hardcoded strings flagged in LOTUS_BUGS.md (Localization rows)
in t() via react-i18next, and adds the keys to public/locales/en.json
under the existing Organisms.* namespace. de.json intentionally left to
fall back to en for now (fallbackLng: 'en') rather than fabricate
translations.

Files: CreateRoomTypeSelector, ImageViewer, MsgTypeRenderers (MLocation),
Reply (ThreadIndicator), ImageContent, DeviceVerification (5 subcomponents),
UrlPreviewCard (DiscordCard), InviteUserPrompt, UploadBoard, PasswordStage.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/url-preview/UrlPreviewCard.tsx

@@ -1,4 +1,5 @@
 import React, { useCallback, useEffect, useRef, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { IPreviewUrlResponse } from 'matrix-js-sdk';
 import { Box, Icon, IconButton, Icons, Scroll, Spinner, Text, as, color, config } from 'folds';
 import { ImageOverlay } from '../ImageOverlay';
@@ -1343,6 +1344,7 @@ function WikipediaCard({ url, prev }: { url: string; prev: IPreviewUrlResponse }
 }
 
 function DiscordCard({ url, prev }: { url: string; prev: IPreviewUrlResponse }) {
+  const { t } = useTranslation();
   const title = prev['og:title'] ?? '';
   const description = prev['og:description'] ?? '';
   const iconUrl = (prev['og:image'] as string | undefined) ?? '';
@@ -1383,7 +1385,9 @@ function DiscordCard({ url, prev }: { url: string; prev: IPreviewUrlResponse })
           priority="300"
         >
           <SiteBadge label="Discord" colorClass={previewCss.BadgeDiscord} />
-          <span style={{ marginLeft: '6px', opacity: 0.7, fontSize: '0.85em' }}>Join Server</span>
+          <span style={{ marginLeft: '6px', opacity: 0.7, fontSize: '0.85em' }}>
+            {t('Organisms.UrlPreview.join_server')}
+          </span>
         </Text>
         {title && (
           <Text truncate priority="400">