fix: comprehensive i18n — replace hardcoded French/English strings with t() calls

Replaced ~100+ hardcoded French and English text strings across 30+ components
with proper i18n t() calls. Added 57 new translation keys to all 15 locale files
(ar, de, en, es, fa, fr, hi, it, ja, ko, nl, pl, pt, ru, zh).

Key changes:
- contextual-ai-chat.tsx: 30 French strings → t() (actions, toasts, labels, placeholders)
- ai-chat.tsx: 15 French/English strings → t() (header, tabs, welcome, insights, history)
- note-inline-editor.tsx: 20 French fallbacks removed (toolbar, save status, checklist)
- lab-skeleton.tsx: French loading text → t()
- admin-header.tsx, header.tsx, editor-connections-section.tsx: French fallbacks removed
- New AI chat component, agent cards, sidebar, settings panel i18n cleanup

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/components/lab/lab-skeleton.tsx

@@ -1,8 +1,10 @@
 'use client'
 
 import { Skeleton } from "@/components/ui/skeleton"
+import { useLanguage } from '@/lib/i18n'
 
 export function LabSkeleton() {
+  const { t } = useLanguage()
   return (
     <div className="flex-1 w-full h-full bg-slate-50 dark:bg-[#1a1c22] relative overflow-hidden">
       {/* Mesh grid background simulation */}
@@ -31,8 +33,8 @@ export function LabSkeleton() {
         <div className="flex flex-col items-center gap-4 bg-white/80 dark:bg-[#252830]/80 p-8 rounded-3xl border shadow-2xl backdrop-blur-xl animate-in fade-in zoom-in duration-500">
           <div className="w-16 h-16 border-4 border-primary border-t-transparent rounded-full animate-spin" />
           <div className="flex flex-col items-center gap-1">
-            <h3 className="font-bold text-lg">Initialisation de l'espace</h3>
-            <p className="text-sm text-muted-foreground animate-pulse">Chargement de vos idées...</p>
+            <h3 className="font-bold text-lg">{t('lab.initializing')}</h3>
+            <p className="text-sm text-muted-foreground animate-pulse">{t('lab.loadingIdeas')}</p>
           </div>
         </div>
       </div>