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/relay.html

@@ -8,7 +8,7 @@
 </div>
 
 <div class="card" style="text-align:center;padding:48px 24px;">
-  <div style="font-size:40px;line-height:1;margin-bottom:12px;">🔀</div>
+  <div style="font-size:40px;line-height:1;margin-bottom:12px;"><i class="fa-solid fa-shuffle"></i></div>
   <strong>{{ title }} — coming soon</strong>
   <p class="muted" style="margin-top:8px;">This relay isn’t implemented yet.</p>
 </div>