refactor: implement user deletion functionality and enhance settings management

frontend/src/lib/timezones.ts

@@ -0,0 +1,26 @@
+export const fallbackTimezones = [
+  "America/Los_Angeles",
+  "America/Denver",
+  "America/Chicago",
+  "America/New_York",
+  "America/Sao_Paulo",
+  "Europe/London",
+  "Europe/Berlin",
+  "Europe/Paris",
+  "Asia/Dubai",
+  "Asia/Kolkata",
+  "Asia/Singapore",
+  "Asia/Tokyo",
+  "Australia/Sydney",
+];
+
+export function getSupportedTimezones(): string[] {
+  if (typeof Intl !== "undefined" && "supportedValuesOf" in Intl) {
+    return (
+      Intl as typeof Intl & { supportedValuesOf: (key: string) => string[] }
+    )
+      .supportedValuesOf("timeZone")
+      .sort();
+  }
+  return fallbackTimezones;
+}