feat(frontend): redesign homepage and file config form with aurora palette

Rebuild the visual identity from the actual Ombrora mark (violet/cyan aurora
blobs) instead of the generic blue/amber scheme, add Bricolage Grotesque and
IBM Plex Mono for display and code-like text, and give the hero an animated
aurora backdrop, gradient headline, and a format-pair marquee driven by the
real registered converters.

Rework the file config form: target format and icon size are both chip
groups now instead of a native select, and quality/compression sliders get a
gradient-filled track, custom thumb, and a mono value pill to match. File
type icons are color-coded by family (images/documents/fonts/ebooks) and
reused across FileConfigCard, FileCard, and FormatsGrid.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/ReassuranceStrip.jsx

@@ -1,5 +1,7 @@
+import { useEffect, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 import { Clock, LockKey, CloudArrowUp, HardDrives } from '@phosphor-icons/react';
+import { fetchConfig } from '../api.js';
 
 const ITEMS = [
   { key: 'autoDelete', Icon: Clock },
@@ -10,14 +12,29 @@ const ITEMS = [
 
 export function ReassuranceStrip() {
   const { t } = useTranslation();
+  const [config, setConfig] = useState(null);
+
+  useEffect(() => {
+    fetchConfig().then(setConfig).catch(() => {});
+  }, []);
+
+  if (!config) return null;
+
+  const values = {
+    autoDelete: config.retentionHours,
+    maxSize: config.maxFileSizeMb,
+  };
+
   return (
     <section className="reassurance">
       <h2>{t('reassurance.title')}</h2>
       <ul className="reassurance-list">
         {ITEMS.map(({ key, Icon }) => (
           <li key={key}>
-            <Icon size={24} weight="regular" />
-            <span>{t(`reassurance.${key}`)}</span>
+            <span className="reassurance-icon">
+              <Icon size={22} weight="regular" />
+            </span>
+            <span>{t(`reassurance.${key}`, { value: values[key] })}</span>
           </li>
         ))}
       </ul>