Refactor user settings

Use resources instead of custom controllers, following the Rails way
and making things much cleaner in the process.

app/views/settings/_account.html.erb

@@ -0,0 +1,19 @@
+<section>
+  <h3>E-Mail</h3>
+  <p class="mb-2">
+    <%= label :email, 'Address', class: 'font-bold' %>
+  </p>
+  <p class="flex gap-1 mb-2 sm:w-3/5">
+    <input type="text" id="email" class="grow"
+           value=<%= current_user.email %> disabled="disabled" />
+  </p>
+</section>
+<section>
+  <h3>Password</h3>
+  <p class="mb-8">Use the following button to request an email with a password reset link:</p>
+  <%= form_with(url: reset_password_settings_path, method: :post) do %>
+    <p>
+      <%= submit_tag("Send me a password reset link", class: 'btn-md btn-gray w-full sm:w-auto') %>
+    </p>
+  <% end %>
+</section>