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/components/AnimatedPanel.tsx

@@ -0,0 +1,54 @@
+import { useEffect, useRef, useState, type ReactNode } from "react";
+
+interface AnimatedPanelProps {
+  open: boolean;
+  children: ReactNode;
+  className?: string;
+  /** Duration in ms for the exit animation before unmounting. */
+  exitDuration?: number;
+}
+
+export function AnimatedPanel({ open, children, className, exitDuration = 140 }: AnimatedPanelProps) {
+  const [mounted, setMounted] = useState(open);
+  const [visible, setVisible] = useState(open);
+  const timerRef = useRef<number | null>(null);
+
+  useEffect(() => {
+    if (open) {
+      if (timerRef.current) {
+        window.clearTimeout(timerRef.current);
+        timerRef.current = null;
+      }
+      setMounted(true);
+      requestAnimationFrame(() => {
+        requestAnimationFrame(() => {
+          setVisible(true);
+        });
+      });
+    } else {
+      setVisible(false);
+      timerRef.current = window.setTimeout(() => {
+        setMounted(false);
+        timerRef.current = null;
+      }, exitDuration);
+    }
+  }, [open, exitDuration]);
+
+  useEffect(() => {
+    return () => {
+      if (timerRef.current) {
+        window.clearTimeout(timerRef.current);
+      }
+    };
+  }, []);
+
+  if (!mounted) return null;
+
+  return (
+    <div
+      className={`${className ?? ""} animated-panel${visible ? " is-visible" : ""}`}
+    >
+      {children}
+    </div>
+  );
+}