fix: shorten the Pull Requests tab to "PRs" in repository detail

The repository detail uses a four-segment control (Code, Issues,
Pull Requests, Actions). "Pull Requests" dominated the width,
squeezed the other segments, and truncated on narrower iPhones.
"PRs" balances the segments and keeps them legible.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Forji/Forji/Views/RepositoryDetailView.swift

@@ -30,7 +30,7 @@ struct RepositoryDetailView: View {
     enum DetailTab: String {
         case code = "Code"
         case issues = "Issues"
-        case pulls = "Pull Requests"
+        case pulls = "PRs"
         case actions = "Actions"
 
         var icon: String {