fix: brainstorm infinite loop, ghost cursor, embedding ::vector cast, semantic search, billing stats, usage meter accordion

- Fix useBrainstormSocket: stable guestId via useRef, remove setState in cleanup
- Fix GhostCursor: direct DOM manipulation via refs, no useState re-renders
- Fix all SQL embedding queries: add ::vector cast on text columns
- Fix embedding truncation to 15000 chars (under 8192 token limit)
- Fix NoteEmbedding INSERT: remove non-existent updatedAt column
- Fix billing page: show all quota stats in grid instead of single metric
- Fix usage meter: accordion expand/collapse, per-feature detail
- Fix semantic search: rebuild 103 note embeddings, ::vector cast on vectorSearch
- Fix brainstorm expand/manual-idea/create: ::vector cast on embedding SQL

memento-note/components/settings/SettingsNav.tsx

@@ -28,12 +28,12 @@ export function SettingsNav({ className }: SettingsNavProps) {
   const isActive = (href: string) => pathname === href || pathname.startsWith(href + '/')
 
   return (
-    <nav className={`flex items-center gap-1 border-b border-border/40 pb-px ${className || ''}`}>
+    <nav className={`flex flex-wrap items-center gap-1 border-b border-border/40 pb-px ${className || ''}`}>
       {tabs.map((tab) => (
         <Link
           key={tab.id}
           href={tab.href}
-          className="flex items-center gap-2.5 px-6 py-5 text-[10px] font-bold uppercase tracking-[0.18em] transition-all relative whitespace-nowrap text-concrete hover:text-ink/60"
+          className="flex items-center gap-2.5 px-4 py-3 text-[10px] font-bold uppercase tracking-[0.18em] transition-all relative whitespace-nowrap text-concrete hover:text-ink/60"
           style={{ color: isActive(tab.href) ? 'var(--ink)' : undefined }}
         >
           <span style={{ color: isActive(tab.href) ? 'var(--ink)' : 'var(--concrete)' }}>{tab.icon}</span>