feat: add state widgets (EmptyState, ErrorState) with PageStandards

lib/src/widgets/states/empty_state.dart

@@ -0,0 +1,78 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:mom_kitchen/src/standards/page_standards.dart';
+import 'package:mom_kitchen/src/widgets/base/standard_button.dart';
+
+class EmptyState extends StatelessWidget {
+  final String? title;
+  final String? message;
+  final IconData? icon;
+  final String? emoji;
+  final String? buttonText;
+  final VoidCallback? onButtonPressed;
+
+  const EmptyState({
+    super.key,
+    this.title,
+    this.message,
+    this.icon,
+    this.emoji,
+    this.buttonText,
+    this.onButtonPressed,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final standards = PageStandards.of(context);
+    final l10n = standards.l10n;
+
+    return Center(
+      child: Padding(
+        padding: standards.scaledPadding(EdgeInsets.all(32)),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            if (emoji != null)
+              Text(
+                emoji!,
+                style: TextStyle(fontSize: standards.scaledFontSize(64)),
+              )
+            else
+              Icon(
+                icon ?? CupertinoIcons.cube_box,
+                size: standards.scaledFontSize(64),
+                color: standards.textColor.withOpacity(0.4),
+              ),
+            SizedBox(height: standards.scaledHeight(16)),
+            Text(
+              title ?? l10n.noData,
+              style: standards.textStyle.copyWith(
+                fontSize: standards.fontSize + 4,
+                fontWeight: FontWeight.w600,
+              ),
+              textAlign: TextAlign.center,
+            ),
+            if (message != null) ...[
+              SizedBox(height: standards.scaledHeight(8)),
+              Text(
+                message!,
+                style: standards.textStyle.copyWith(
+                  color: standards.textColor.withOpacity(0.6),
+                ),
+                textAlign: TextAlign.center,
+              ),
+            ],
+            if (buttonText != null && onButtonPressed != null) ...[
+              SizedBox(height: standards.scaledHeight(24)),
+              StandardButton(
+                text: buttonText!,
+                onPressed: onButtonPressed,
+                type: StandardButtonType.primary,
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}

lib/src/widgets/states/error_state.dart

@@ -0,0 +1,52 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:mom_kitchen/src/standards/page_standards.dart';
+import 'package:mom_kitchen/src/widgets/base/standard_button.dart';
+
+class ErrorState extends StatelessWidget {
+  final String message;
+  final VoidCallback? onRetry;
+  final String? retryText;
+
+  const ErrorState({
+    super.key,
+    required this.message,
+    this.onRetry,
+    this.retryText,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final standards = PageStandards.of(context);
+    final l10n = standards.l10n;
+
+    return Center(
+      child: Padding(
+        padding: standards.scaledPadding(EdgeInsets.all(32)),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Text(
+              '⚠️',
+              style: TextStyle(fontSize: standards.scaledFontSize(64)),
+            ),
+            SizedBox(height: standards.scaledHeight(16)),
+            Text(
+              message,
+              style: standards.textStyle,
+              textAlign: TextAlign.center,
+            ),
+            if (onRetry != null) ...[
+              SizedBox(height: standards.scaledHeight(24)),
+              StandardButton(
+                text: retryText ?? l10n.retry,
+                onPressed: onRetry,
+                type: StandardButtonType.outline,
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}