UI redesign Phase 1: NavigationSplitView with collapsible sidebar

- Replace root VStack with NavigationSplitView (2-column, collapsible sidebar)
- Add SidebarView: new chat button, conversation search, list with swipe actions
- Slim HeaderView to text-only (provider + model + star); remove all icon rows
- Move status pills (Online, MCP, Synced) to footer right side
- Remove version number and shortcut hints from footer
- Add resizable InputBar with drag handle (persisted height) and globe/network.slash online toggle
- Fix Norwegian menu appearing on English systems (CFBundleLocalizations in Info.plist)
- Add View menu (Model Info, History, Stats, Credits, Online Mode toggle ⌘⇧O)
- Add ⌘L as alias for Search Conversations (muscle memory for /load users)
- Add Check for Updates to Help menu with download URL from Gitea API
- Add one-time Intel/Rosetta deprecation warning on first launch
- Swift 6: fix self.Self.isoString() call sites in DatabaseService

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

oAI.xcodeproj/xcshareddata/xcschemes/oAI.xcscheme

@@ -34,7 +34,7 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      language = "nb"
+      language = "en"
       launchStyle = "0"
       useCustomWorkingDirectory = "NO"
       ignoresPersistentStateOnLaunch = "NO"