chore: rewrite user-facing JS messages in Www module

Conservative cleanup of frappe.throw/msgprint messages per the message style
guide; meaning, severity, and .format() arguments are unchanged:

- index bare {} placeholders as {0}/{1}/... so translators can reorder
- move f-strings / .format() / concatenation out of _() (they break gettext
  extraction and never translate)
- wrap translatable dynamic values (DocType/Select labels) in _()
- fix grammar and colloquialisms
- drop no-op _() wrapping runtime-built strings

Part of #53976.

erpnext/www/book_appointment/index.js

@@ -234,7 +234,7 @@ async function submit() {
 			if (response.message.status == "Unverified") {
 				frappe.show_alert(__("Please check your email to confirm the appointment"));
 			} else {
-				frappe.show_alert(__("Appointment Created Successfully"));
+				frappe.show_alert(__("Appointment created successfully"));
 			}
 			setTimeout(() => {
 				let redirect_url = "/";
@@ -245,7 +245,7 @@ async function submit() {
 			}, 5000);
 		},
 		error: (err) => {
-			frappe.show_alert(__("Something went wrong please try again"));
+			frappe.show_alert(__("Something went wrong, please try again"));
 			button.disabled = false;
 		},
 	});