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/features/community/CommunityPage.tsx

@@ -477,8 +477,9 @@ function CommunityPage({ projects, isAuthenticated, onStartCreate, onOpenProject
                   <div className="community-card-actions">
                     <button
                       type="button"
-                      className={isFavorite ? "is-active" : ""}
+                      className={isFavorite ? "is-active heart-animate" : ""}
                       aria-pressed={isFavorite}
+                      key={isFavorite ? `fav-${cardId}` : `unfav-${cardId}`}
                       onClick={(event) => {
                         event.stopPropagation();
                         void handleToggleFavorite(item, cardId);