refactor(ui): remaster settings and navigation layout

- Update navigation labels from "My Account" to "Dashboard" and "Login" to "Sign in", updating tests accordingly.
- Redesign settings forms into structured sections with improved spacing and layout.
- Add CSS styles for tabs, small buttons, and responsive settings sections to enhance the user experience.

backend/templates/layouts/base.html

@@ -28,11 +28,13 @@
       </a>
       <div class="nav-links">
         {{if .CurrentUser}}
+        <a class="button button-ghost" href="/app">Dashboard</a>
+        {{if eq .CurrentUser.Role "admin"}}<a class="button button-ghost" href="/admin">Admin</a>{{end}}
         <a class="button button-ghost" href="/api">API</a>
-        <a class="button button-outline" href="/account/settings">My Account</a>
+        <a class="button button-outline" href="/account/settings"><span class="nav-username">{{.CurrentUser.Username}}</span></a>
         {{else}}
-        <a class="button button-ghost" href="/login">Login</a>
         <a class="button button-ghost" href="/api">API</a>
+        <a class="button button-outline" href="/login">Sign in</a>
         {{end}}
       </div>
     </nav>
@@ -44,7 +46,7 @@
 
   <footer class="site-footer">
     <span>{{.AppName}} · {{.CurrentYear}} · self-hosted</span>
-    <span class="footer-links">{{if .CurrentUser}}<a href="/api">API</a><a href="/account/settings">My Account</a>{{else}}<a href="/login">Login</a><a href="/api">API</a>{{end}}</span>
+    <span class="footer-links">{{if .CurrentUser}}<a href="/app">Dashboard</a><a href="/api">API</a><a href="/account/settings">Account</a>{{else}}<a href="/login">Sign in</a><a href="/api">API</a>{{end}}</span>
   </footer>
 </body>
 </html>