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/ViewModels/ChatViewModel.swift

@@ -1313,7 +1313,7 @@ Don't narrate future actions ("Let me...") - just use the tools.
                 // Append the complete system prompt (default + custom)
                 systemContent += "\n\n---\n\n" + effectiveSystemPrompt
 
-                var messagesToSend: [Message] = memoryEnabled
+                let messagesToSend: [Message] = memoryEnabled
                     ? messages.filter { $0.role != .system }
                     : [messages.last(where: { $0.role == .user })].compactMap { $0 }
 
@@ -1659,7 +1659,7 @@ Don't narrate future actions ("Let me...") - just use the tools.
                 if isOverloaded && attempt < maxAttempts && !Task.isCancelled {
                     let delay = Double(1 << attempt) // 2s, 4s, 8s
                     Log.api.warning("API overloaded, retrying in \(Int(delay))s (attempt \(attempt)/\(maxAttempts - 1))...")
-                    await MainActor.run {
+                    _ = await MainActor.run {
                         showSystemMessage("⏳ API overloaded, retrying in \(Int(delay))s… (attempt \(attempt)/\(maxAttempts - 1))")
                     }
                     try await Task.sleep(nanoseconds: UInt64(delay * 1_000_000_000))