Fix OAuth mobile app support with custom URL schemes

- Configure Doorkeeper to allow custom URL schemes (maybeapp://)
- Disable force_ssl_in_redirect_uri to support non-HTTPS schemes
- Add custom Doorkeeper views with mobile OAuth detection
- Disable Turbo for mobile OAuth flows to prevent redirect interference
- Add display parameter preservation through OAuth flow
- Create custom Doorkeeper layouts with proper styling
- Add comprehensive integration tests for mobile OAuth flows
- Ensure all OAuth pages use proper doorkeeper/application layout

This allows the mobile app to complete OAuth authorization flows
without the web app interfering with custom URL scheme redirects.

🤖 Generated with Claude Code

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

app/views/doorkeeper/authorized_applications/_delete_form.html.erb

@@ -0,0 +1,4 @@
+<%- submit_btn_css ||= 'btn btn-link' %>
+<%= form_tag oauth_authorized_application_path(application), method: :delete do %>
+  <%= submit_tag t('doorkeeper.authorized_applications.buttons.revoke'), onclick: "return confirm('#{ t('doorkeeper.authorized_applications.confirmations.revoke') }')", class: submit_btn_css %>
+<% end %>

app/views/doorkeeper/authorized_applications/index.html.erb

@@ -0,0 +1,24 @@
+<header class="page-header">
+  <h1><%= t('doorkeeper.authorized_applications.index.title') %></h1>
+</header>
+
+<main role="main">
+  <table class="table table-striped">
+    <thead>
+    <tr>
+      <th><%= t('doorkeeper.authorized_applications.index.application') %></th>
+      <th><%= t('doorkeeper.authorized_applications.index.created_at') %></th>
+      <th></th>
+    </tr>
+    </thead>
+    <tbody>
+    <% @applications.each do |application| %>
+      <tr>
+        <td><%= application.name %></td>
+        <td><%= application.created_at.strftime(t('doorkeeper.authorized_applications.index.date_format')) %></td>
+        <td><%= render 'delete_form', application: application %></td>
+      </tr>
+    <% end %>
+    </tbody>
+  </table>
+</main>