fix: force en-US locale in Intl formatters to ensure consistent date and time output

frontend/src/utils/dateFormat.ts

@@ -1,13 +1,13 @@
-const timeFormatter = new Intl.DateTimeFormat(undefined, {
+const timeFormatter = new Intl.DateTimeFormat("en-US", {
   timeStyle: "short",
 });
 
-const dateTimeFormatter = new Intl.DateTimeFormat(undefined, {
+const dateTimeFormatter = new Intl.DateTimeFormat("en-US", {
   dateStyle: "medium",
   timeStyle: "short",
 });
 
-const rtf = new Intl.RelativeTimeFormat(undefined, {
+const rtf = new Intl.RelativeTimeFormat("en-US", {
   numeric: "auto",
 });
 

frontend/vitest.config.ts

@@ -8,7 +8,6 @@ export default defineConfig({
   test: {
     env: {
       VITE_API_URL: "http://piku-server",
-      TZ: "Asia/Kolkata",
     },
     include: ["**/*.test.ts"],
     environment: "jsdom",