feat(juice): button press feedback + fade screen transitions

Adds PressableScale (0.94 squish on tap-down) around the Adventure
FilledButton, Classic OutlinedButton, and each season-map stage node.
Replaces all in-app MaterialPageRoute pushes with a gentle fade+scale
PageRouteBuilder (320ms in, 240ms out) via a new fadeRoute helper.

lib/ui/widgets/fade_route.dart

@@ -0,0 +1,22 @@
+// lib/ui/widgets/fade_route.dart
+import 'package:flutter/material.dart';
+
+/// A gentle fade(+slight scale) page transition for in-app navigation.
+Route<T> fadeRoute<T>(Widget page) {
+  return PageRouteBuilder<T>(
+    transitionDuration: const Duration(milliseconds: 320),
+    reverseTransitionDuration: const Duration(milliseconds: 240),
+    pageBuilder: (_, _, _) => page,
+    transitionsBuilder: (_, animation, _, child) {
+      final curved =
+          CurvedAnimation(parent: animation, curve: Curves.easeOutCubic);
+      return FadeTransition(
+        opacity: curved,
+        child: ScaleTransition(
+          scale: Tween(begin: 0.98, end: 1.0).animate(curved),
+          child: child,
+        ),
+      );
+    },
+  );
+}

lib/ui/widgets/pressable_scale.dart

@@ -0,0 +1,37 @@
+// lib/ui/widgets/pressable_scale.dart
+import 'package:flutter/material.dart';
+
+/// Wraps a tappable child with a quick scale-down on press for tactile feel.
+/// If [onTap] is provided it handles the tap; otherwise the child's own
+/// gesture/button handles it and this only adds the visual squish.
+class PressableScale extends StatefulWidget {
+  const PressableScale({super.key, required this.child, this.onTap});
+
+  final Widget child;
+  final VoidCallback? onTap;
+
+  @override
+  State<PressableScale> createState() => _PressableScaleState();
+}
+
+class _PressableScaleState extends State<PressableScale> {
+  bool _down = false;
+  void _set(bool v) => setState(() => _down = v);
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      behavior: HitTestBehavior.opaque,
+      onTapDown: (_) => _set(true),
+      onTapUp: (_) => _set(false),
+      onTapCancel: () => _set(false),
+      onTap: widget.onTap,
+      child: AnimatedScale(
+        scale: _down ? 0.94 : 1.0,
+        duration: const Duration(milliseconds: 90),
+        curve: Curves.easeOut,
+        child: widget.child,
+      ),
+    );
+  }
+}