feat: Sprint 3 — delight, polish, and responsive sidebar

Celebration micro-interactions:
- SuccessToast: auto-dismissing pill toast (success/info/warning variants)
- ConfettiBurst: pure CSS 20-particle confetti on project creation
- Project wizard: confetti + toast on successful creation
- Vacation approval/rejection: contextual toasts
- Allocation status change: success toast
- Button: active:scale-[0.97] press feedback on all variants

Collapsible sidebar + responsive:
- Desktop: toggle collapse (72px icons-only mode) with localStorage persistence
- NavTooltip: hover labels on collapsed icons
- Mobile: hamburger menu + slide-in overlay with backdrop
- Auto-close sidebar on mobile navigation
- Scroll-to-top on route change (smooth behavior)

Hover polish + accessibility:
- Table rows: animated left-border accent + hover-lift
- Stat cards + widgets: hover elevation + border glow
- Timeline blocks: scale(1.02) + shadow-md on hover
- Smooth scroll globally with prefers-reduced-motion fallback
- Filter chips: framer-motion scale+fade enter/exit
- Dropdowns: scaleY origin-top reveal animation
- Preferences modal: scale+fade entrance
- Link underline: animated ::after width expansion on hover

Co-Authored-By: claude-flow <ruv@ruv.net>

packages/ui/src/components/Button.tsx

@@ -30,8 +30,9 @@ export function Button({
   return (
     <button
       className={clsx(
-        "inline-flex items-center justify-center font-medium rounded-lg transition-colors",
+        "inline-flex items-center justify-center font-medium rounded-lg transition-all duration-75",
         "focus:outline-none focus:ring-2 focus:ring-brand-500 focus:ring-offset-2",
+        "active:scale-[0.97]",
         "disabled:opacity-50 disabled:cursor-not-allowed",
         variantClasses[variant],
         sizeClasses[size],