Frontend revamp: Animal Crossing × Claude design with shadcn components

- New palette: deep nook green sidebar, sage user bubbles, warm cream answer cards
- shadcn-style UI primitives: Button (CVA variants), Textarea, Input, Badge, Table
- cn() utility (clsx + tailwind-merge)
- lucide-react icons throughout (no more text-only buttons)
- Simba mode: custom CSS toggle switch
- Send button: circular amber button with arrow icon
- AnswerBubble: amber gradient accent bar, loading dots animation
- QuestionBubble: sage green pill with rounded-3xl
- ToolBubble: centered leaf-green badge pill
- ConversationList: active item highlighting, proper selectedId prop
- Sidebar: collapsible with PanelLeftClose/Open icons, icon-only collapsed state
- LoginScreen: decorative background blobs, refined rounded card
- AdminPanel: proper icon buttons, leaf-green save confirmation
- Fonts: Playfair Display (brand) + Nunito 800 weight added

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

raggr-frontend/src/lib/utils.ts

@@ -0,0 +1,6 @@
+import { clsx, type ClassValue } from "clsx";
+import { twMerge } from "tailwind-merge";
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs));
+}