feat: 新增 AppLoadingIndicator 和 AppPressable 组件

- 新增 AppLoadingIndicator 加载指示器组件
- 新增 AppPressable 按压反馈组件
- 新增 AppSheetInputField 输入框组件
- 更新 AppButton 和其他共享组件

apps/lib/shared/widgets/page_header.dart

@@ -17,6 +17,7 @@ class PageHeader extends StatelessWidget {
         padding: const EdgeInsets.symmetric(horizontal: 20),
         child: Row(
           mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          crossAxisAlignment: CrossAxisAlignment.center,
           children: [
             leading ?? const SizedBox.shrink(),
             trailing ?? const SizedBox.shrink(),
@@ -27,30 +28,91 @@ class PageHeader extends StatelessWidget {
   }
 }
 
-class BackButton extends StatelessWidget {
+class BackButton extends StatefulWidget {
   final VoidCallback? onPressed;
 
   const BackButton({super.key, this.onPressed});
 
+  @override
+  State<BackButton> createState() => _BackButtonState();
+}
+
+class _BackButtonState extends State<BackButton> {
+  bool _isPressed = false;
+
   @override
   Widget build(BuildContext context) {
-    return SizedBox(
-      width: AppSpacing.xxl * 2,
-      height: AppSpacing.xxl * 2,
-      child: TextButton(
-        onPressed: onPressed ?? () => Navigator.of(context).pop(),
-        style: TextButton.styleFrom(
-          padding: const EdgeInsets.all(AppSpacing.none),
-          backgroundColor: AppColors.surfaceTertiary,
-          shape: RoundedRectangleBorder(
-            borderRadius: BorderRadius.circular(AppRadius.full),
-            side: const BorderSide(color: AppColors.borderTertiary),
-          ),
+    final background = _isPressed ? AppColors.surfaceInfo : AppColors.white;
+    final borderColor = _isPressed
+        ? AppColors.borderQuaternary
+        : AppColors.borderTertiary;
+
+    return AnimatedScale(
+      scale: _isPressed ? 0.96 : 1,
+      duration: const Duration(milliseconds: 110),
+      curve: Curves.easeOut,
+      child: AnimatedContainer(
+        duration: const Duration(milliseconds: 110),
+        decoration: BoxDecoration(
+          color: background,
+          borderRadius: BorderRadius.circular(AppRadius.full),
+          border: Border.all(color: borderColor),
+          boxShadow: _isPressed
+              ? const []
+              : [
+                  const BoxShadow(
+                    color: AppColors.white,
+                    blurRadius: AppRadius.sm,
+                    offset: Offset(0, -1),
+                  ),
+                  BoxShadow(
+                    color: AppColors.slate200.withValues(alpha: 0.42),
+                    blurRadius: AppRadius.md,
+                    offset: const Offset(0, AppSpacing.xs),
+                  ),
+                ],
         ),
-        child: const Icon(
-          Icons.chevron_left,
-          size: AppSpacing.lg + AppSpacing.xs,
-          color: AppColors.slate700,
+        child: SizedBox(
+          width: AppSpacing.xl * 2,
+          height: AppSpacing.xl * 2,
+          child: Material(
+            color: Colors.transparent,
+            child: InkWell(
+              borderRadius: BorderRadius.circular(AppRadius.full),
+              onTap: widget.onPressed ?? () => Navigator.of(context).pop(),
+              onTapDown: (_) {
+                if (_isPressed) {
+                  return;
+                }
+                setState(() {
+                  _isPressed = true;
+                });
+              },
+              onTapCancel: () {
+                if (!_isPressed) {
+                  return;
+                }
+                setState(() {
+                  _isPressed = false;
+                });
+              },
+              onTapUp: (_) {
+                if (!_isPressed) {
+                  return;
+                }
+                setState(() {
+                  _isPressed = false;
+                });
+              },
+              child: Center(
+                child: Icon(
+                  Icons.chevron_left,
+                  size: AppSpacing.lg + AppSpacing.xs,
+                  color: _isPressed ? AppColors.blue600 : AppColors.slate700,
+                ),
+              ),
+            ),
+          ),
         ),
       ),
     );