Add in-app diagnostic logging + resilient inbox; bump to 1.2

- LogStore: bounded in-memory + persisted log of API calls and errors,
  viewable and shareable from Settings → View logs.
- GiteaClient: log every request/response status (esp. 404s).
- Inbox: a single failing repo no longer wipes the whole inbox — per-repo
  errors are caught, logged, and the rest still load.
- Bump to 1.2 so SideStore offers the update.

GiteaPR/Settings/SettingsView.swift

@@ -51,6 +51,12 @@ struct SettingsView: View {
                         .foregroundColor(.secondary)
                 }
 
+                Section("Diagnostics") {
+                    NavigationLink("View logs") {
+                        LogsView()
+                    }
+                }
+
                 Section {
                     Button("Log out", role: .destructive) {
                         showLogoutConfirm = true