feat: design system overhaul — sidebar, AI chats, settings, brainstorm, color cleanup

- Sidebar: dynamic brand-accent colors, brainstorm section restyled
- AI chat general: popup panel with expand/collapse, hides when contextual AI open
- AI chat contextual: tabs reordered (Actions first), X close button, height fix
- Settings: all tabs restyled, 6 new color presets (sage, terracotta, iron, etc.)
- Global color cleanup: emerald/orange hardcoded → brand-accent dynamic
- Brainstorm page: orange → brand-accent throughout
- PageEntry animation component added to key pages
- Floating AI button: bg-brand-accent instead of hardcoded black
- i18n: all 15 locales updated with new AI/billing keys
- Billing: freemium quota tracking, BYOK, stripe subscription scaffolding
- Admin: integrated into new design
- AGENTS.md + CLAUDE.md project rules added

memento-note/app/(main)/settings/mcp/page.tsx

@@ -2,6 +2,7 @@ import { auth } from '@/auth'
 import { redirect } from 'next/navigation'
 import { McpSettingsPanel } from '@/components/mcp/mcp-settings-panel'
 import { listMcpKeys, getMcpServerStatus } from '@/app/actions/mcp-keys'
+import { useLanguage } from '@/lib/i18n'
 
 export default async function McpSettingsPage() {
   const session = await auth()
@@ -14,9 +15,9 @@ export default async function McpSettingsPage() {
 
   return (
     <div className="space-y-8">
-      <p className="text-[11px] font-bold uppercase tracking-[0.2em] text-muted-foreground">
+      <h3 className="text-[10px] font-bold uppercase tracking-[0.3em] text-concrete">
         Gérez vos clés API et serveurs MCP connectés.
-      </p>
+      </h3>
       <McpSettingsPanel initialKeys={keys} serverStatus={serverStatus} />
     </div>
   )