Refactor screens to MVC architecture with modular widgets

- Extract business logic from screens into dedicated controllers
- Split large screen files into smaller, reusable widget components
- Add controllers for AddSubscriptionScreen and DetailScreen
- Create modular widgets for subscription and detail features
- Improve code organization and maintainability
- Remove duplicated code and improve reusability

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/widgets/common/form_fields/base_text_field.dart

@@ -0,0 +1,145 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+/// 공통 텍스트 필드 위젯
+/// 프로젝트 전체에서 일관된 스타일의 텍스트 입력 필드를 제공합니다.
+class BaseTextField extends StatelessWidget {
+  final TextEditingController controller;
+  final FocusNode? focusNode;
+  final String? label;
+  final String? hintText;
+  final TextInputAction? textInputAction;
+  final TextInputType? keyboardType;
+  final List<TextInputFormatter>? inputFormatters;
+  final Function()? onTap;
+  final Function()? onEditingComplete;
+  final Function(String)? onChanged;
+  final String? Function(String?)? validator;
+  final bool enabled;
+  final Widget? prefixIcon;
+  final String? prefixText;
+  final Widget? suffixIcon;
+  final bool obscureText;
+  final int? maxLines;
+  final int? minLines;
+  final bool readOnly;
+  final TextStyle? style;
+  final EdgeInsetsGeometry? contentPadding;
+  final Color? fillColor;
+  final Color? cursorColor;
+
+  const BaseTextField({
+    super.key,
+    required this.controller,
+    this.focusNode,
+    this.label,
+    this.hintText,
+    this.textInputAction = TextInputAction.next,
+    this.keyboardType,
+    this.inputFormatters,
+    this.onTap,
+    this.onEditingComplete,
+    this.onChanged,
+    this.validator,
+    this.enabled = true,
+    this.prefixIcon,
+    this.prefixText,
+    this.suffixIcon,
+    this.obscureText = false,
+    this.maxLines = 1,
+    this.minLines,
+    this.readOnly = false,
+    this.style,
+    this.contentPadding,
+    this.fillColor,
+    this.cursorColor,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        if (label != null) ...[
+          Text(
+            label!,
+            style: TextStyle(
+              fontSize: 16,
+              fontWeight: FontWeight.w600,
+              color: theme.colorScheme.onSurface,
+            ),
+          ),
+          const SizedBox(height: 8),
+        ],
+        TextFormField(
+          controller: controller,
+          focusNode: focusNode,
+          textInputAction: textInputAction,
+          keyboardType: keyboardType,
+          inputFormatters: inputFormatters,
+          onTap: onTap,
+          onEditingComplete: onEditingComplete,
+          onChanged: onChanged,
+          validator: validator,
+          enabled: enabled,
+          obscureText: obscureText,
+          maxLines: maxLines,
+          minLines: minLines,
+          readOnly: readOnly,
+          cursorColor: cursorColor ?? theme.primaryColor,
+          style: style ?? TextStyle(
+            fontSize: 16,
+            color: theme.colorScheme.onSurface,
+          ),
+          decoration: InputDecoration(
+            hintText: hintText,
+            hintStyle: TextStyle(
+              color: theme.colorScheme.onSurface.withOpacity(0.6),
+            ),
+            prefixIcon: prefixIcon,
+            prefixText: prefixText,
+            suffixIcon: suffixIcon,
+            filled: true,
+            fillColor: fillColor ?? Colors.white,
+            contentPadding: contentPadding ?? const EdgeInsets.all(16),
+            border: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide.none,
+            ),
+            focusedBorder: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide(
+                color: theme.primaryColor,
+                width: 2,
+              ),
+            ),
+            enabledBorder: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide.none,
+            ),
+            disabledBorder: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide.none,
+            ),
+            errorBorder: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide(
+                color: theme.colorScheme.error,
+                width: 1,
+              ),
+            ),
+            focusedErrorBorder: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(16),
+              borderSide: BorderSide(
+                color: theme.colorScheme.error,
+                width: 2,
+              ),
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}