feat: major platform expansion — Brain service, RSS reader, iOS app, AI assistants, Firefox extension

Brain Service:
- Playwright stealth crawler replacing browserless (og:image, Readability, Reddit JSON API)
- AI classification with tag definitions and folder assignment
- YouTube video download via yt-dlp
- Karakeep migration complete (96 items)
- Taxonomy management (folders with icons/colors, tags)
- Discovery shuffle, sort options, search (Meilisearch + pgvector)
- Item tag/folder editing, card color accents

RSS Reader Service:
- Custom FastAPI reader replacing Miniflux
- Feed management (add/delete/refresh), category support
- Full article extraction via Readability
- Background content fetching for new entries
- Mark all read with confirmation
- Infinite scroll, retention cleanup (30/60 day)
- 17 feeds migrated from Miniflux

iOS App (SwiftUI):
- Native iOS 17+ app with @Observable architecture
- Cookie-based auth, configurable gateway URL
- Dashboard with custom background photo + frosted glass widgets
- Full fitness module (today/templates/goals/food library)
- AI assistant chat (fitness + brain, raw JSON state management)
- 120fps ProMotion support

AI Assistants (Gateway):
- Unified dispatcher with fitness/brain domain detection
- Fitness: natural language food logging, photo analysis, multi-item splitting
- Brain: save/append/update/delete notes, search & answer, undo support
- Madiha user gets fitness-only (brain disabled)

Firefox Extension:
- One-click save to Brain from any page
- Login with platform credentials
- Right-click context menu (save page/link/image)
- Notes field for URL saves
- Signed and published on AMO

Other:
- Reader bookmark button routes to Brain (was Karakeep)
- Fitness food library with "Add" button + add-to-meal popup
- Kindle send file size check (25MB SMTP2GO limit)
- Atelier UI as default (useAtelierShell=true)
- Mobile upload box in nav drawer

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend-v2/src/app.css

@@ -12,8 +12,9 @@
    ═══════════════════════════════════════════════ */
 
 @layer base {
-  html, body { overflow-x: hidden; }
-  body { padding-top: env(safe-area-inset-top); padding-bottom: env(safe-area-inset-bottom); }
+  html { background-color: #f5efe6; }
+  body { overflow-x: clip; }
+  body { padding-bottom: env(safe-area-inset-bottom); }
   :root {
     /* ── Fonts ── */
     --font: 'Outfit', -apple-system, system-ui, sans-serif;
@@ -106,7 +107,7 @@
 
   /* ── LIGHT MODE — Zinc + Emerald ── */
   :root {
-    --canvas: #FAFAFA;
+    --canvas: #f5efe6;
     --surface: #FFFFFF;
     --surface-secondary: #F4F4F5;
     --card: #FFFFFF;