refactor: Move widgets to lib

lib/widgets/layouts/one_page_card.dart

@@ -0,0 +1,45 @@
+import 'dart:math';
+
+import 'package:flutter/material.dart';
+
+class OnePageCard extends StatelessWidget {
+  final Widget child;
+
+  const OnePageCard({Key key, this.child}) : super(key: key);
+
+  static const int alpha = 12;
+  static const int breakpoint = 600;
+  @override
+  Widget build(BuildContext context) {
+    return MediaQuery.of(context).size.width <= breakpoint ||
+            MediaQuery.of(context).size.height <= breakpoint
+        ? child
+        : Container(
+            decoration: BoxDecoration(
+              color: Theme.of(context).backgroundColor,
+              gradient: LinearGradient(
+                begin: Alignment.topRight,
+                end: Alignment.bottomLeft,
+                stops: [
+                  0.1,
+                  0.4,
+                  0.6,
+                  0.9,
+                ],
+                colors: [
+                  Theme.of(context).secondaryHeaderColor.withAlpha(alpha),
+                  Theme.of(context).primaryColor.withAlpha(alpha),
+                  Theme.of(context).accentColor.withAlpha(alpha),
+                  Theme.of(context).backgroundColor.withAlpha(alpha),
+                ],
+              ),
+            ),
+            padding: EdgeInsets.symmetric(
+              horizontal:
+                  max((MediaQuery.of(context).size.width - 600) / 2, 12),
+              vertical: max((MediaQuery.of(context).size.height - 800) / 2, 12),
+            ),
+            child: SafeArea(child: Card(child: child)),
+          );
+  }
+}