feat: App mobile Expo + API mobile dédiée

memento-mobile/ (Expo + React Native + expo-router):
- Auth: login email/password → Bearer token (expo-secure-store)
- Layout: guard auth → redirect /(auth)/login ou /(tabs)/home
- Tabs: Accueil, Carnets, Recherche, Profil
- Screens: login, home (recent notes + quick actions), notebooks list,
  note viewer (WebView HTML), search (texte), notebook detail, profile
- Design: tokens brand-accent (#A47148), ink, concrete, paper, border
- lib/config.ts: API_URL dev/prod configurable
- lib/api.ts: apiFetch avec Bearer token automatique
- lib/store.ts: Zustand auth store (login/logout/restore)

memento-note/ (API mobile dédiée):
- lib/mobile-auth.ts: createMobileToken / verifyMobileToken (HMAC-SHA256, 90j)
- POST /api/mobile/auth/login: email+password → token + user
- GET /api/mobile/auth/me: valider token, retourner profil
- GET /api/mobile/notebooks: liste carnets avec nb notes
- GET /api/mobile/notes: notes récentes (filtre par carnet optionnel)
- GET /api/mobile/notes/[id]: contenu complet d'une note
- GET /api/mobile/search: recherche fulltext titre+contenu

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memento-note/components/settings/settings-help-box.tsx

@@ -21,29 +21,29 @@ export function SettingsHelpBox({ title, steps, defaultOpen = false, className }
   const [open, setOpen] = useState(defaultOpen)
 
   return (
-    <div className={cn('rounded-xl border border-blue-200/60 dark:border-blue-800/30 bg-blue-50/50 dark:bg-blue-950/10 overflow-hidden', className)}>
+    <div className={cn('rounded-xl border border-border/50 bg-border/5 overflow-hidden', className)}>
       <button
         type="button"
         onClick={() => setOpen((v) => !v)}
-        className="w-full flex items-center gap-2 px-4 py-3 text-left hover:bg-blue-100/40 dark:hover:bg-blue-900/10 transition-colors"
+        className="w-full flex items-center gap-2 px-4 py-3 text-left hover:bg-border/10 transition-colors"
       >
-        <HelpCircle size={14} className="text-blue-500 dark:text-blue-400 shrink-0" />
-        <span className="text-[12px] font-semibold text-blue-700 dark:text-blue-300 flex-1">{title}</span>
+        <HelpCircle size={14} className="text-brand-accent shrink-0" />
+        <span className="text-[12px] font-semibold text-ink flex-1">{title}</span>
         {open ? (
-          <ChevronUp size={13} className="text-blue-400 shrink-0" />
+          <ChevronUp size={13} className="text-concrete shrink-0" />
         ) : (
-          <ChevronDown size={13} className="text-blue-400 shrink-0" />
+          <ChevronDown size={13} className="text-concrete shrink-0" />
         )}
       </button>
 
       {open && (
-        <ol className="px-4 pb-4 space-y-2">
+        <ol className="px-4 pb-4 space-y-2.5 border-t border-border/30 pt-3">
           {steps.map((step, i) => (
             <li key={i} className="flex items-start gap-2.5">
-              <span className="w-5 h-5 rounded-full bg-blue-100 dark:bg-blue-900/40 text-blue-600 dark:text-blue-300 text-[10px] font-bold flex items-center justify-center shrink-0 mt-0.5">
+              <span className="w-5 h-5 rounded-full bg-brand-accent/10 text-brand-accent text-[10px] font-bold flex items-center justify-center shrink-0 mt-0.5">
                 {step.icon ?? i + 1}
               </span>
-              <span className="text-[12px] text-blue-800 dark:text-blue-200 leading-relaxed">
+              <span className="text-[12px] text-concrete leading-relaxed">
                 {step.text}
                 {step.link && (
                   <>
@@ -52,7 +52,7 @@ export function SettingsHelpBox({ title, steps, defaultOpen = false, className }
                       href={step.link.href}
                       target="_blank"
                       rel="noopener noreferrer"
-                      className="inline-flex items-center gap-0.5 underline underline-offset-2 font-medium hover:text-blue-600"
+                      className="inline-flex items-center gap-0.5 text-brand-accent underline underline-offset-2 font-medium hover:opacity-80"
                     >
                       {step.link.label}
                       <ExternalLink size={10} />