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>

apps/web/src/components/dashboard/WidgetContainer.tsx

@@ -15,8 +15,8 @@ export function WidgetContainer({ title, onRemove, children, isDragging }: Widge
       initial={{ opacity: 0, y: 16 }}
       animate={{ opacity: 1, y: 0 }}
       transition={{ duration: 0.35, ease: "easeOut" }}
-      className={`flex flex-col h-full bg-white rounded-xl border border-gray-200 shadow-sm overflow-hidden ${
-        isDragging ? "shadow-lg border-brand-300" : ""
+      className={`flex flex-col h-full bg-white rounded-xl border border-gray-200 shadow-sm overflow-hidden transition-colors duration-200 ${
+        isDragging ? "shadow-lg border-brand-300" : "hover:border-brand-200 dark:hover:border-brand-800"
       }`}
     >
       {/* Header */}

apps/web/src/components/dashboard/widgets/StatCardsWidget.tsx

@@ -44,7 +44,7 @@ function StatCard({
   return (
     <FadeIn delay={delay} direction="up">
       <div
-        className={`rounded-2xl border border-gray-200 bg-white/80 p-4 shadow-sm dark:border-gray-700 dark:bg-gray-900/70 ${
+        className={`rounded-2xl border border-gray-200 bg-white/80 p-4 shadow-sm dark:border-gray-700 dark:bg-gray-900/70 hover-lift cursor-default ${
           accentColor ? `border-l-[3px] ${accentBorder}` : ""
         }`}
       >