feat(ui): forge icons on repo cards (github, gitea, mozilla)

Add SVG icons for each forge before the repo name on dashboard cards.
Icons sourced from user-provided SVGs in ui/public/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/App.css

@@ -105,6 +105,14 @@ a.hot-pink {
   font-size: 0.9rem;
 }
 
+.forge-icon {
+  width: 16px;
+  height: 16px;
+  margin-right: 6px;
+  vertical-align: -2px;
+  opacity: 0.7;
+}
+
 .project-card a {
   color: #ff4081;
 }