handlers: Fix off-by-one in previous endpoint

Fixes an off-by-one comparison in the previous endpoint that prevented
the second site in the order (list index #1) from ever redirecting to
the first (list index #0).

Signed-off-by: Taavi Väänänen <hi@taavi.wtf>

mention prefix for emailed patches

Add static file server

Implements: https://todo.sr.ht/~amolith/public-tracker/23

Check whether validation has already run today

resolve -h conflict and remove follow func

correct example domain (again)

correct example domain

document host flag and improve validation docs

document validation

remove printing report to console

reword unknown error

ignore validation log

remove unnecessary printing

add validation logic

add justfile and lint config

use constants rather than magic numbers

simplify code and handle errors

remove copyright years

Replace hardcoded contact email with flag

update wakapi shield for cumulative time