UI: Font Awesome icons, Material touches, 3-line collapse button

Swap all emoji icons for Font Awesome (sidebar, homepage tiles, profile/chat/
list/settings/relay actions); add Roboto font + card elevation hover for a
Material feel. Replace the bottom 'Collapse' pill with a 3-line (fa-bars) toggle
in the sidebar header; remove the old collapse pill CSS/JS. Copy buttons toggle
FA check/copy via innerHTML. Plain text status (✓/✗) and back arrows kept.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

manager/templates/settings.html

@@ -100,7 +100,7 @@
       </div>
       <div class="theme-label">
         <span>Original Light</span>
-        <span class="checkmark">✓</span>
+        <span class="checkmark"><i class="fa-solid fa-check"></i></span>
       </div>
     </div>
 
@@ -113,7 +113,7 @@
       </div>
       <div class="theme-label">
         <span>Original Dark</span>
-        <span class="checkmark">✓</span>
+        <span class="checkmark"><i class="fa-solid fa-check"></i></span>
       </div>
     </div>
 
@@ -126,7 +126,7 @@
       </div>
       <div class="theme-label">
         <span>Matrix</span>
-        <span class="checkmark">✓</span>
+        <span class="checkmark"><i class="fa-solid fa-check"></i></span>
       </div>
     </div>