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/note-card.tsx

@@ -132,13 +132,13 @@ function getInitials(name: string): string {
 function getAvatarColor(name: string): string {
   const colors = [
     'bg-primary',
-    'bg-purple-500',
-    'bg-green-500',
-    'bg-orange-500',
-    'bg-pink-500',
-    'bg-teal-500',
-    'bg-red-500',
-    'bg-indigo-500',
+    'bg-purple-600',
+    'bg-emerald-600',
+    'bg-amber-600',
+    'bg-pink-600',
+    'bg-teal-600',
+    'bg-blue-600',
+    'bg-indigo-600',
   ]
 
   const hash = name.split('').reduce((acc, char) => acc + char.charCodeAt(0), 0)
@@ -404,14 +404,13 @@ export const NoteCard = memo(function NoteCard({
       }}
       onDragEnd={() => onDragEnd?.()}
       className={cn(
-        'note-card group relative rounded-2xl overflow-hidden p-5 border shadow-sm',
+        'note-card group relative rounded-lg overflow-hidden p-6 border-transparent shadow-sm',
         'transition-all duration-200 ease-out',
-        'hover:shadow-xl hover:-translate-y-1',
+        'hover:shadow-md hover:border-border/50 hover:-translate-y-0.5',
         colorClasses.bg,
         colorClasses.card,
         colorClasses.hover,
-        colorClasses.hover,
-        isDragging && 'shadow-2xl' // Removed opacity, scale, and rotation for clean drag
+        isDragging && 'shadow-lg'
       )}
       onClick={(e) => {
         // Only trigger edit if not clicking on buttons
@@ -474,7 +473,7 @@ export const NoteCard = memo(function NoteCard({
         size="sm"
         data-testid="pin-button"
         className={cn(
-          "absolute top-2 right-12 z-20 min-h-[44px] min-w-[44px] h-8 w-8 p-0 rounded-md transition-opacity",
+          "absolute top-2 right-12 z-20 h-8 w-8 p-0 rounded-md transition-opacity",
           optimisticNote.isPinned ? "opacity-100" : "opacity-0 group-hover:opacity-100"
         )}
         onClick={(e) => {
@@ -513,7 +512,7 @@ export const NoteCard = memo(function NoteCard({
 
       {/* Title */}
       {optimisticNote.title && (
-        <h3 className="text-base font-medium mb-2 pr-10 text-foreground">
+        <h3 className="text-lg font-heading font-semibold mb-2 pr-20 text-foreground leading-tight tracking-tight">
           {optimisticNote.title}
         </h3>
       )}
@@ -587,7 +586,10 @@ export const NoteCard = memo(function NoteCard({
       {/* Content */}
       {optimisticNote.type === 'text' ? (
         <div className="text-sm text-foreground line-clamp-10">
-          <MarkdownContent content={optimisticNote.content} />
+          <MarkdownContent 
+            content={optimisticNote.content} 
+            className="prose-h1:text-xl prose-h1:font-semibold prose-h1:leading-snug prose-h1:mt-1 prose-h1:mb-2 prose-h2:text-lg prose-h2:font-medium prose-h3:text-base prose-p:text-sm prose-p:leading-relaxed"
+          />
         </div>
       ) : (
         <NoteChecklist