feat: implement preview work units preference with local storage support

wwwroot/theme.js

@@ -55,4 +55,35 @@ window.workTrackerTheme = (() => {
     };
 })();
 
+window.workTrackerPreferences = {
+    getBool(key) {
+        try {
+            const value = localStorage.getItem(key);
+            if (value === null) {
+                return null;
+            }
+
+            if (value === "true") {
+                return true;
+            }
+
+            if (value === "false") {
+                return false;
+            }
+
+            return null;
+        }
+        catch {
+            return null;
+        }
+    },
+    setBool(key, value) {
+        try {
+            localStorage.setItem(key, value ? "true" : "false");
+        }
+        catch {
+        }
+    }
+};
+
 window.workTrackerTheme.init();