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/Views/Main/ChatView.swift

@@ -37,10 +37,6 @@ struct ChatView: View {
             HeaderView(
                 provider: viewModel.currentProvider,
                 model: viewModel.selectedModel,
-                stats: viewModel.sessionStats,
-                onlineMode: viewModel.onlineMode,
-                mcpEnabled: viewModel.mcpEnabled,
-                mcpStatus: viewModel.mcpStatus,
                 onModelSelect: onModelSelect,
                 onProviderChange: onProviderChange
             )
@@ -85,10 +81,13 @@ struct ChatView: View {
             InputBar(
                 text: $viewModel.inputText,
                 isGenerating: viewModel.isGenerating,
-                mcpStatus: viewModel.mcpStatus,
                 onlineMode: viewModel.onlineMode,
                 onSend: viewModel.sendMessage,
-                onCancel: viewModel.cancelGeneration
+                onCancel: viewModel.cancelGeneration,
+                onToggleOnline: {
+                    viewModel.onlineMode.toggle()
+                    SettingsService.shared.onlineMode = viewModel.onlineMode
+                }
             )
 
             // Footer
@@ -96,7 +95,9 @@ struct ChatView: View {
                 stats: viewModel.sessionStats,
                 conversationName: viewModel.currentConversationName,
                 hasUnsavedChanges: viewModel.hasUnsavedChanges,
-                onQuickSave: viewModel.quickSave
+                onQuickSave: viewModel.quickSave,
+                onlineMode: viewModel.onlineMode,
+                mcpEnabled: viewModel.mcpEnabled
             )
         }
         .background(Color.oaiBackground)