cleanup: regroup constants used across the client

Before adding more options, regroup existing client-side preferences

Refs #71614

Change-Id: Iacf2fdadb54d33551b07108911288ba3f86b36fc
diff --git a/src/GeneralPrefsVC.mm b/src/GeneralPrefsVC.mm
index ea6d972..4bc2b3b 100644
--- a/src/GeneralPrefsVC.mm
+++ b/src/GeneralPrefsVC.mm
@@ -31,6 +31,8 @@
 
 #import <categorizedhistorymodel.h>
 
+#import "Constants.h"
+
 @interface GeneralPrefsVC ()
 @property (assign) IBOutlet NSTextField *historyChangedLabel;
 
@@ -44,7 +46,7 @@
 - (void)loadView
 {
     [super loadView];
-    [[NSUserDefaults standardUserDefaults] addObserver:self forKeyPath:@"history_limit" options:NSKeyValueObservingOptionNew context:NULL];
+    [[NSUserDefaults standardUserDefaults] addObserver:self forKeyPath:Preferences::HistoryLimit options:NSKeyValueObservingOptionNew context:NULL];
 }
 
 - (IBAction)clearHistory:(id)sender {