Merge spinner + swipeable PR sections; bump to 3.1

- MergeSheet: show a spinner in the toolbar while the merge is confirming/
  rejecting, lock Cancel and interactive dismissal during the request, and
  prevent double-taps.
- PR detail: replace the ScrollView-switch with a page-style TabView so you
  can swipe left/right to change sections (iOS 26 style); bottom bar taps
  still select. Make DetailTab Hashable. Bump to 3.1.

GiteaPR/Detail/PRDetailView.swift

@@ -11,7 +11,7 @@ struct PRDetailView: View {
     @State private var requestChangesMode = false
     @State private var showMergeSuccess = false
 
-    enum DetailTab: String, CaseIterable, Identifiable {
+    enum DetailTab: String, CaseIterable, Identifiable, Hashable {
         case overview = "Overview"
         case conversation = "Conversation"
         case files = "Files"
@@ -103,14 +103,20 @@ struct PRDetailView: View {
         VStack(spacing: 0) {
             header(pr)
 
-            ScrollView {
-                switch selectedTab {
-                case .overview: OverviewTab(pr: pr)
-                case .conversation: ConversationTab(vm: vm)
-                case .files: FilesTab(vm: vm)
-                case .checks: ChecksTab(vm: vm, onRerun: { showRerunConfirm = $0 })
-                }
+            // Page-style TabView gives iOS-native swipe-to-change between
+            // sections (matching iOS 26), while the bottom bar taps select.
+            TabView(selection: $selectedTab) {
+                OverviewTab(pr: pr)
+                    .tag(DetailTab.overview)
+                ConversationTab(vm: vm)
+                    .tag(DetailTab.conversation)
+                FilesTab(vm: vm)
+                    .tag(DetailTab.files)
+                ChecksTab(vm: vm, onRerun: { showRerunConfirm = $0 })
+                    .tag(DetailTab.checks)
             }
+            .tabViewStyle(.page(indexDisplayMode: .never))
+            .ignoresSafeArea(edges: .bottom)
 
             bottomTabBar
         }