Switch the UI icons from mynaui to TDesign

Swap @ng-icons/mynaui for @ng-icons/tdesign-icons (34.0.0, the release
matching @ng-icons/core), drawn at TDesign's native stroke. Each former
mynaui name maps to one TDesign name everywhere it was used; the unused
ArrowLeftRight is dropped. The options button's ellipsis goes from 1.5rem
to 0.8rem: TDesign's dots span 18 of 24 units against mynaui's 8, so this
keeps today's footprint.

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

ui/src/app/skins/shadlike/context-menu.ts

@@ -62,7 +62,7 @@ const EDGE_GAP = 6; // px on purpose: a viewport-edge margin, not a UI size
             >
               <span class="w-3.5 shrink-0">
                 @if (item.checked) {
-                  <ng-icon name="mynaCheck" size="0.85rem" class="text-primary" />
+                  <ng-icon name="tdesignCheck" size="0.85rem" class="text-primary" />
                 }
               </span>
               <span class="flex-1 truncate">{{ item.label }}</span>