feat(core): add theme, shared widgets and validators

apps/lib/shared/widgets/app_button.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+import '../../core/theme/design_tokens.dart';
+
+class AppButton extends StatelessWidget {
+  final String text;
+  final VoidCallback? onPressed;
+  final bool isPrimary;
+  final bool isOutlined;
+  final double height;
+  final bool isLoading;
+
+  const AppButton({
+    super.key,
+    required this.text,
+    this.onPressed,
+    this.isPrimary = true,
+    this.isOutlined = false,
+    this.height = 44,
+    this.isLoading = false,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    if (isOutlined) {
+      return SizedBox(
+        height: height,
+        child: OutlinedButton(
+          onPressed: isLoading ? null : onPressed,
+          style: OutlinedButton.styleFrom(
+            backgroundColor: AppColors.background,
+            foregroundColor: AppColors.slate500,
+            side: const BorderSide(color: AppColors.input),
+            shape: RoundedRectangleBorder(
+              borderRadius: BorderRadius.circular(AppRadius.sm),
+            ),
+          ),
+          child: isLoading
+              ? const SizedBox(
+                  width: 16,
+                  height: 16,
+                  child: CircularProgressIndicator(strokeWidth: 2),
+                )
+              : Text(
+                  text,
+                  style: const TextStyle(
+                    fontSize: 13,
+                    fontWeight: FontWeight.w500,
+                  ),
+                ),
+        ),
+      );
+    }
+
+    return SizedBox(
+      height: height,
+      child: ElevatedButton(
+        onPressed: isLoading ? null : onPressed,
+        child: isLoading
+            ? const SizedBox(
+                width: 16,
+                height: 16,
+                child: CircularProgressIndicator(
+                  strokeWidth: 2,
+                  color: AppColors.primaryForeground,
+                ),
+              )
+            : Text(
+                text,
+                style: const TextStyle(
+                  fontSize: 14,
+                  fontWeight: FontWeight.w500,
+                ),
+              ),
+      ),
+    );
+  }
+}

apps/lib/shared/widgets/app_input.dart

@@ -0,0 +1,51 @@
+import 'package:flutter/material.dart';
+import '../../core/theme/design_tokens.dart';
+
+class AppInput extends StatelessWidget {
+  final String label;
+  final String hint;
+  final TextEditingController? controller;
+  final bool obscureText;
+  final TextInputType? keyboardType;
+  final Widget? suffix;
+  final int? maxLines;
+  final bool enabled;
+
+  const AppInput({
+    super.key,
+    required this.label,
+    required this.hint,
+    this.controller,
+    this.obscureText = false,
+    this.keyboardType,
+    this.suffix,
+    this.maxLines = 1,
+    this.enabled = true,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          label,
+          style: const TextStyle(
+            fontSize: 13,
+            fontWeight: FontWeight.w500,
+            color: AppColors.slate600,
+          ),
+        ),
+        const SizedBox(height: 6),
+        TextField(
+          controller: controller,
+          obscureText: obscureText,
+          keyboardType: keyboardType,
+          maxLines: maxLines,
+          enabled: enabled,
+          decoration: InputDecoration(hintText: hint, suffixIcon: suffix),
+        ),
+      ],
+    );
+  }
+}

apps/lib/shared/widgets/page_header.dart

@@ -0,0 +1,53 @@
+import 'package:flutter/material.dart';
+
+class PageHeader extends StatelessWidget {
+  final Widget? leading;
+  final Widget? trailing;
+  final double height;
+
+  const PageHeader({super.key, this.leading, this.trailing, this.height = 64});
+
+  @override
+  Widget build(BuildContext context) {
+    return SizedBox(
+      height: height,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 20),
+        child: Row(
+          mainAxisAlignment: MainAxisAlignment.spaceBetween,
+          children: [
+            leading ?? const SizedBox.shrink(),
+            trailing ?? const SizedBox.shrink(),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class BackButton extends StatelessWidget {
+  final VoidCallback? onPressed;
+
+  const BackButton({super.key, this.onPressed});
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: onPressed ?? () => Navigator.of(context).pop(),
+      child: Container(
+        width: 36,
+        height: 36,
+        decoration: BoxDecoration(
+          color: const Color(0xFFF8FAFF),
+          borderRadius: BorderRadius.circular(18),
+          border: Border.all(color: const Color(0xFFDEE7F6)),
+        ),
+        child: const Icon(
+          Icons.chevron_left,
+          size: 18,
+          color: Color(0xFF334155),
+        ),
+      ),
+    );
+  }
+}

apps/lib/shared/widgets/warning_banner.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+import '../../core/theme/design_tokens.dart';
+
+class WarningBanner extends StatelessWidget {
+  final String message;
+  final bool visible;
+
+  const WarningBanner({super.key, required this.message, this.visible = true});
+
+  @override
+  Widget build(BuildContext context) {
+    if (!visible) return const SizedBox.shrink();
+
+    return Container(
+      width: double.infinity,
+      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
+      decoration: BoxDecoration(
+        color: AppColors.warningBackground,
+        borderRadius: BorderRadius.circular(AppRadius.sm),
+      ),
+      child: Row(
+        children: [
+          const Icon(
+            Icons.warning_amber_rounded,
+            size: 16,
+            color: AppColors.warningText,
+          ),
+          const SizedBox(width: 8),
+          Expanded(
+            child: Text(
+              message,
+              style: const TextStyle(
+                fontSize: 13,
+                color: AppColors.warningText,
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}