feat: design system overhaul — sidebar, AI chats, settings, brainstorm, color cleanup

- Sidebar: dynamic brand-accent colors, brainstorm section restyled
- AI chat general: popup panel with expand/collapse, hides when contextual AI open
- AI chat contextual: tabs reordered (Actions first), X close button, height fix
- Settings: all tabs restyled, 6 new color presets (sage, terracotta, iron, etc.)
- Global color cleanup: emerald/orange hardcoded → brand-accent dynamic
- Brainstorm page: orange → brand-accent throughout
- PageEntry animation component added to key pages
- Floating AI button: bg-brand-accent instead of hardcoded black
- i18n: all 15 locales updated with new AI/billing keys
- Billing: freemium quota tracking, BYOK, stripe subscription scaffolding
- Admin: integrated into new design
- AGENTS.md + CLAUDE.md project rules added

memento-note/components/auto-label-suggestion-dialog.tsx

@@ -134,8 +134,8 @@ export function AutoLabelSuggestionDialog({
             <DialogTitle className="sr-only">{t('ai.autoLabels.analyzing')}</DialogTitle>
           </DialogHeader>
           <div className="flex flex-col items-center justify-center py-12">
-            <div className="w-16 h-16 rounded-full border border-dashed border-memento-blue/20 flex items-center justify-center mb-4">
-              <Loader2 className="h-6 w-6 animate-spin text-memento-blue" />
+            <div className="w-16 h-16 rounded-full border border-dashed border-brand-accent/20 flex items-center justify-center mb-4">
+              <Loader2 className="h-6 w-6 animate-spin text-brand-accent" />
             </div>
             <p className="text-[10px] text-muted-foreground uppercase tracking-widest font-bold">
               {t('ai.autoLabels.analyzing')}
@@ -155,7 +155,7 @@ export function AutoLabelSuggestionDialog({
       <DialogContent className="max-w-md">
         <DialogHeader>
           <DialogTitle className="flex items-center gap-2">
-            <Sparkles className="h-5 w-5 text-memento-blue" />
+            <Sparkles className="h-5 w-5 text-brand-accent" />
             {t('ai.autoLabels.title')}
           </DialogTitle>
           <DialogDescription>
@@ -175,7 +175,7 @@ export function AutoLabelSuggestionDialog({
                 className={cn(
                   "flex items-start gap-3 p-3 rounded-xl border cursor-pointer transition-all",
                   isSelected
-                    ? "bg-memento-blue/5 border-memento-blue/30 hover:bg-memento-blue/10"
+                    ? "bg-brand-accent/5 border-brand-accent/30 hover:bg-brand-accent/10"
                     : "border-border hover:bg-muted/50"
                 )}
                 onClick={() => toggleLabelSelection(label.name)}
@@ -183,22 +183,22 @@ export function AutoLabelSuggestionDialog({
                 <div className={cn(
                   "w-5 h-5 rounded-full border-2 flex items-center justify-center mt-0.5 transition-all shrink-0",
                   isSelected
-                    ? "bg-memento-blue border-memento-blue"
+                    ? "bg-brand-accent border-brand-accent"
                     : "border-border"
                 )}>
                   {isSelected && <CheckCircle2 className="h-3.5 w-3.5 text-white" />}
                 </div>
                 <div className="flex-1 min-w-0">
                   <div className="flex items-center gap-2">
-                    <Tag className="h-3.5 w-3.5 text-memento-blue/60" />
+                    <Tag className="h-3.5 w-3.5 text-brand-accent/60" />
                     <span className="font-medium text-sm">{label.name}</span>
-                    <Sparkles className="h-3 w-3 text-memento-blue/40" />
+                    <Sparkles className="h-3 w-3 text-brand-accent/40" />
                   </div>
                   <div className="flex items-center gap-3 mt-1.5">
                     <span className="text-[10px] text-muted-foreground">
                       {t('ai.autoLabels.notesCount', { count: label.count })}
                     </span>
-                    <span className="text-[10px] px-2 py-0.5 rounded-full bg-memento-blue/10 text-memento-blue font-bold">
+                    <span className="text-[10px] px-2 py-0.5 rounded-full bg-brand-accent/10 text-brand-accent font-bold">
                       {Math.round(label.confidence * 100)}%
                     </span>
                   </div>
@@ -219,7 +219,7 @@ export function AutoLabelSuggestionDialog({
           <button
             onClick={handleCreateLabels}
             disabled={selectedLabels.size === 0 || creating}
-            className="flex-1 py-3 bg-memento-blue text-white rounded-xl text-[10px] font-bold uppercase tracking-widest hover:opacity-90 transition-all shadow-lg shadow-memento-blue/20 disabled:opacity-50"
+            className="flex-1 py-3 bg-brand-accent text-white rounded-xl text-[10px] font-bold uppercase tracking-widest hover:opacity-90 transition-all shadow-lg shadow-brand-accent/20 disabled:opacity-50"
           >
             {creating ? (
               <span className="flex items-center justify-center gap-2">