feat: UI interaction polish — exit animations, hover effects, directional transitions

- Add AnimatedPanel component with CSS transition-based enter/exit for
  Profile popover and Notification panel (140ms scale+fade)
- Add nav-activate-pulse animation for floating-nav active indicator (320ms glow)
- Add tool-panel-fade-in crossfade when switching ecommerce tools
- Add carousel-card-label slide-up-in 260ms on active carousel card
- Add feature-visual img hover scale(1.03)+brightness, experience-route hover translateY(-2px)
- Add community-case-card--mosaic hover scale(1.02)+shadow lift
- Add directional PageTransition: forward→slideX(20px), backward→slideX(-20px)
- Move vite proxy target from hardcoded IP to VITE_DEV_PROXY env variable
- Add .env.example for developer onboarding

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

src/styles/components/page-transition.css

@@ -15,3 +15,56 @@
     transform: translateY(0);
   }
 }
+
+/* Directional page transitions */
+.page-motion--enter.is-forward {
+  animation: page-slide-in-forward 200ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
+.page-motion--enter.is-backward {
+  animation: page-slide-in-backward 200ms var(--ease-out-expo, cubic-bezier(0.16, 1, 0.3, 1)) both;
+}
+
+.page-motion--exit.is-forward {
+  animation: page-slide-out-forward 180ms ease both;
+}
+
+.page-motion--exit.is-backward {
+  animation: page-slide-out-backward 180ms ease both;
+}
+
+@keyframes page-slide-in-forward {
+  from {
+    opacity: 0;
+    transform: translateX(20px);
+  }
+  to {
+    opacity: 1;
+    transform: translateX(0);
+  }
+}
+
+@keyframes page-slide-in-backward {
+  from {
+    opacity: 0;
+    transform: translateX(-20px);
+  }
+  to {
+    opacity: 1;
+    transform: translateX(0);
+  }
+}
+
+@keyframes page-slide-out-forward {
+  to {
+    opacity: 0;
+    transform: translateX(-16px);
+  }
+}
+
+@keyframes page-slide-out-backward {
+  to {
+    opacity: 0;
+    transform: translateX(16px);
+  }
+}