feat: UI animation enhancements across all major pages

P1 - Critical UX feedback:
- Add scale-in + slide-up-in entrance animations to profile popover and notification panel
- Port SmoothedProgressBar to EcommercePage (4 generation tools: clone, detail, tryOn, productSet)
- Add result-reveal stagger animation to ecommerce result grids
- Add heart-pop spring animation to CommunityPage favorite toggle

P2 - Visual polish:
- Add scroll-entrance IntersectionObserver animations for HomePage feature sections and experience section
- Add chat-message-in entrance animation to WorkbenchPage message rows
- Fix prefers-reduced-motion accessibility in WelcomeSplash canvas (skip animation, instant entry)

P3 - CSS consolidation:
- Remove conflicting .page-motion definition from legacy-pages.css (keep translateY version from legacy-components.css)
- Consolidate skeleton-shimmer: remove opacity-pulse keyframe from primitives.css, unify with gradient sweep
- Wire up --ease-spring token for heart-pop animation
- Add :active press states (scale 0.97) to topbar buttons, brand lockup

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/styles/components/motion.css

@@ -39,6 +39,78 @@
   to { opacity: 1; }
 }
 
+/* Popover / panel entrance utilities */
+.panel-enter {
+  animation: scale-in 150ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both,
+             slide-up-in 150ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
+.backdrop-enter {
+  animation: backdrop-in 140ms ease both;
+}
+
+/* Heart toggle spring animation */
+@keyframes heart-pop {
+  0% { transform: scale(1); }
+  40% { transform: scale(1.3); }
+  70% { transform: scale(0.9); }
+  100% { transform: scale(1); }
+}
+
+.heart-animate {
+  animation: heart-pop 420ms var(--ease-spring, cubic-bezier(0.34, 1.2, 0.64, 1)) both;
+}
+
+/* Result reveal stagger for generation output grids */
+.result-reveal > * {
+  opacity: 0;
+  animation: slide-up-in 320ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
+.result-reveal > *:nth-child(1) { animation-delay: 0ms; }
+.result-reveal > *:nth-child(2) { animation-delay: 80ms; }
+.result-reveal > *:nth-child(3) { animation-delay: 160ms; }
+.result-reveal > *:nth-child(4) { animation-delay: 240ms; }
+.result-reveal > *:nth-child(5) { animation-delay: 320ms; }
+.result-reveal > *:nth-child(n+6) { animation-delay: 400ms; }
+
+/* Scroll-triggered entrance: hidden until revealed by IntersectionObserver */
+.scroll-entrance {
+  opacity: 0;
+  transform: translateY(16px);
+  transition: opacity 480ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)),
+              transform 480ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1));
+}
+
+.scroll-entrance.is-visible {
+  opacity: 1;
+  transform: translateY(0);
+}
+
+.scroll-entrance.is-visible > * {
+  animation: slide-up-in 380ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
+.scroll-entrance.is-visible > *:nth-child(1) { animation-delay: 60ms; }
+.scroll-entrance.is-visible > *:nth-child(2) { animation-delay: 140ms; }
+.scroll-entrance.is-visible > *:nth-child(3) { animation-delay: 220ms; }
+
+/* Chat message entrance animation */
+@keyframes chat-message-in {
+  from {
+    opacity: 0;
+    transform: translateY(10px);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}
+
+.chat-message-enter {
+  animation: chat-message-in 220ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
 /* Stagger utility: apply to parent, children get delayed entrance */
 .motion-stagger > * {
   animation: list-item-in 280ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;