Fix diff screen hang/crash: stable DiffLine id + request timeout; bump to 1.5

DiffLine.id was a computed property returning a fresh UUID() on every access.
SwiftUI's ForEach requires stable identities; regenerating each read churned
the main thread, hanging the diff screen and eventually crashing. Store the
UUID once per line. Also add a 30s URLRequest timeout so a hung request can't
leave the 'Loading diff...' spinner forever. Bump to 1.5.

GiteaPR/Detail/DiffView.swift

@@ -120,7 +120,10 @@ struct DiffView: View {
 private enum DiffLineType { case context, addition, deletion, hunk, meta }
 
 private struct DiffLine: Identifiable {
+    // Stable id: a fresh UUID() on EVERY access (computed property) makes
+    // SwiftUI's ForEach re-identify on every render, churning the main thread
+    // and eventually crashing. Store it once.
+    let id: UUID = UUID()
     let text: String
     let type: DiffLineType
-    var id: UUID { UUID() }
 }