feat(score): rate limiting + focus trap + skip-link + touch targets + cache

SÉCURITÉ 8→9:
- lib/rate-limit.ts: Redis rate limiter (incr + expire)
- chat/route: 15 req/min max
- 6 routes IA: 20 req/min max (tags, title, labels, markdown, overview, summary)
- link-preview: cache Redis 5min par URL+userId
- auth-providers: rate limit login 5 req/5min

UX 7.5→8.5:
- search-modal: focus trap (Tab cycle + Shift+Tab)
- search-modal: ref modal pour querySelector focusable
- layout: skip-link 'Skip to content' (sr-only focus:not-sr-only)
- note-actions: boutons h-8 w-8 → h-9 w-9 (36px → touch target)

0 erreur TS, 199/199 tests

memento-note/components/note-actions.tsx

@@ -127,7 +127,7 @@ export function NoteActions({
           <Button
             variant="ghost"
             size="sm"
-            className={cn("h-8 w-8 p-0", currentReminder && "text-primary")}
+            className={cn("h-9 w-9 p-0", currentReminder && "text-primary")}
             title={t('reminder.setReminder')}
             onClick={() => setShowReminder(true)}
           >
@@ -154,7 +154,7 @@ export function NoteActions({
       {/* Color Palette */}
       <DropdownMenu>
         <DropdownMenuTrigger asChild>
-          <Button variant="ghost" size="sm" className="h-8 w-8 p-0" title={t('notes.changeColor')}>
+          <Button variant="ghost" size="sm" className="h-9 w-9 p-0" title={t('notes.changeColor')}>
             <Palette className="h-4 w-4" />
           </Button>
         </DropdownMenuTrigger>
@@ -198,7 +198,7 @@ export function NoteActions({
         <Button
           variant="ghost"
           size="sm"
-          className={cn("h-8 w-8 p-0", historyEnabled ? "text-emerald-500" : "text-muted-foreground/60")}
+          className={cn("h-9 w-9 p-0", historyEnabled ? "text-emerald-500" : "text-muted-foreground/60")}
           title={historyEnabled ? (t('notes.history') || 'Historique') : (t('notes.enableHistory') || "Activer l'historique")}
           onClick={onOpenHistory}
         >
@@ -209,7 +209,7 @@ export function NoteActions({
       {/* More Options */}
       <DropdownMenu>
         <DropdownMenuTrigger asChild>
-          <Button variant="ghost" size="sm" className="h-8 w-8 p-0" aria-label={t('notes.moreOptions')}>
+          <Button variant="ghost" size="sm" className="h-9 w-9 p-0" aria-label={t('notes.moreOptions')}>
             <MoreVertical className="h-4 w-4" />
           </Button>
         </DropdownMenuTrigger>