Use fullScreenCover for Settings and Accounts on tvOS

- Replace sheet presentation with fullScreenCover for Settings and Accounts views on tvOS
- Add proper background color to Settings and Accounts screens on tvOS
- Clean up trailing whitespace in HomeView

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Shared/Navigation/AccountsView.swift

@@ -3,6 +3,9 @@ import SwiftUI
 struct AccountsView: View {
     @StateObject private var model = AccountsViewModel()
     @Environment(\.presentationMode) private var presentationMode
+    #if os(tvOS)
+    @Environment(\.colorScheme) private var colorScheme
+    #endif
 
     var body: some View {
         #if os(macOS)
@@ -28,6 +31,7 @@ struct AccountsView: View {
             }
             #if os(tvOS)
             .frame(maxWidth: 1000)
+            .background(Color.background(scheme: colorScheme).ignoresSafeArea())
             #endif
         #endif
     }

Shared/Navigation/ContentView.swift

@@ -63,17 +63,29 @@ struct ContentView: View {
                 WelcomeScreen()
             }
         )
+        #if os(tvOS)
+        .fullScreenCover(isPresented: $navigation.presentingSettings) {
+            SettingsView()
+        }
+        #else
         .background(
             EmptyView().sheet(isPresented: $navigation.presentingSettings) {
                 SettingsView()
             }
         )
+        #endif
         .modifier(ImportSettingsSheetViewModifier(isPresented: $navigation.presentingSettingsImportSheet, settingsFile: $navigation.settingsImportURL))
+        #if os(tvOS)
+        .fullScreenCover(isPresented: $navigation.presentingAccounts) {
+            AccountsView()
+        }
+        #else
         .background(
             EmptyView().sheet(isPresented: $navigation.presentingAccounts) {
                 AccountsView()
             }
         )
+        #endif
         .background(
             EmptyView().sheet(isPresented: $navigation.presentingHomeSettings) {
                 #if os(macOS)