Remove global flag on timestamp regex

[wnielson]

The global flag on the TIMESTAMP_REGEX causes the call to TIMESTAMP_REGEX.test(value) to return a different value each time it is executed (regex objects are stateful when they have the global flag set¹). Consider the following code:

const TIMESTAMP_REGEX = /^([0-9]+)-(0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])[Tt]([01][0-9]|2[0-3]):([0-5][0-9]):([0-5][0-9]|60)(\.[0-9]+)?(([Zz])|([\+|\-]([01][0-9]|2[0-3]):[0-5][0-9]))$/g;

const value = "2025-01-10T20:51:45.992Z";

console.log(TIMESTAMP_REGEX.test(value)); // true
console.log(TIMESTAMP_REGEX.test(value)); // false
console.log(TIMESTAMP_REGEX.test(value)); // true
console.log(TIMESTAMP_REGEX.test(value)); // false

When run this outputs:

true
false
true
false

This results in a bug where every other timestamp value is actually saved to the database as a string instead of a Timestamp.