Update OAuth authorization URL (MixinNetwork#287)

Author: YeungKC

lib/ui/page/home/tab_collectibles.dart

@@ -273,8 +273,7 @@ class _UnauthorizedWidget extends StatelessWidget {
           const SizedBox(height: 6),
           TextButton(
             onPressed: () {
-              final uri =
-                  Uri.https('mixin-www.zeromesh.net', 'oauth/authorize', {
+              final uri = Uri.https('mixin.one', 'oauth/authorize', {
                 'client_id': Env.clientId,
                 'scope': authScope,
                 'response_type': 'code',

lib/ui/widget/dialog/contact_selection_widget.dart

@@ -206,8 +206,7 @@ class _UnauthorizedWidget extends StatelessWidget {
           const SizedBox(height: 6),
           TextButton(
             onPressed: () {
-              final uri =
-                  Uri.https('mixin-www.zeromesh.net', 'oauth/authorize', {
+              final uri = Uri.https('mixin.one', 'oauth/authorize', {
                 'client_id': Env.clientId,
                 'scope': authScope,
                 'response_type': 'code',