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/pages/home.html

@@ -3,8 +3,13 @@
 {{define "content"}}
 <section class="upload-view" aria-labelledby="upload-title">
   <div class="hero-copy">
+    {{if .CurrentUser}}
+    <h1 id="upload-title">Upload files.</h1>
+    <p>{{.Data.LimitSummary}}</p>
+    {{else}}
     <h1 id="upload-title">Send a file. Get a link.</h1>
     <p>Anonymous, self-hosted transfers. No account required.</p>
+    {{end}}
   </div>
 
   <form class="upload-panel card" id="upload-form" action="/api/v1/upload" method="post" enctype="multipart/form-data">