feat(ui): overhaul frontend with IMPHNEN visual identity

- Update CSS foundation: HSL→oklch color tokens, Poppins font, new utilities
- Replace Three.js sakura particles with CSS glow orbs
- Rebrand Header with IMPHNEN logo and gradient text
- Update all UI components (Button, Card, Badge, Input, Select, Tabs, Toast)
- Apply IMPHNEN design patterns (glass, gradient, grid) to layout
- Remove all hardcoded #7EC8E3/#FFB7C5/#FCA5A5 references
- Standardize rounded-xl across all components
- Replace emoji toasts with Lucide icons

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

services/frontend/src/widgets/DashboardLayout.tsx

@@ -31,8 +31,12 @@ export function DashboardLayout({
 }: DashboardLayoutProps) {
   return (
     <div className="relative min-h-screen bg-background text-foreground">
-      {/* Sakura particle layer */}
+      {/* Background layers */}
       <ParticleBackground />
+      <div
+        className="fixed inset-0 pointer-events-none grid-pattern opacity-[0.03]"
+        aria-hidden="true"
+      />
 
       <div className="relative flex min-h-screen">
         <Sidebar