Add an optional expiration date column for urls

[evanugarte]

users should be able to specify an expiration for a url. this expiration would exist as a new column in the sqlite database.

if a url was requested and it had a non-null expiration value, and the url is expired, it is deleted from the database and the api returns a 404.

game plan

• clone cleezy and run it on your computer
• follow the how to run guide, make sure you can create and delete urls https://github.com/SCE-Development/cleezy?tab=readme-ov-file#how-to-run
• change /find to in addition to querying the sqlite database, check if the expiration column is not null. if it is not null and the expiration is before the present moment, delete the url, and return a 404 response.