fix: WCAG AA contrast compliance for --text-muted/--text-faint, 12px font floor

Override design system tokens in app root CSS: --text-muted raised to 4.5:1
contrast in both light (#766A5E) and dark (#9A9088) modes; --text-faint dark
mode raised from catastrophic 1.4:1 to 3:1 (#6A6058). Migrate --text-faint
usages on readable text (empty states, italic notes, buttons) to --text-muted.
Raise all 10px and 11px font-size declarations to 12px floor.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/components/AboutMeDialog.module.css

@@ -44,7 +44,7 @@
 }
 
 .sourceNote {
-  font-size: 11px;
+  font-size: 12px;
   color: var(--text-muted);
   font-family: var(--font-mono);
 }

ui/src/components/DeploymentProgress.module.css

@@ -74,7 +74,7 @@
 
 /* Labels */
 .label {
-  font-size: 10px;
+  font-size: 12px;
   color: var(--text-muted);
   text-align: center;
   margin-top: 6px;