Add a button to automatically detect venue timezones based on Lat/Lng

[gregorbg]

There are plenty of libraries that can do time zone lookups out there, but most are either abandoned or carry a ~500MB JSON data file around. The one I chose now is relatively lightweight, but needs native Rust bindings which means we need an additional build tooling dependency in our Docker setups :/

Here's a short video clip of me choosing an obviously wrong time zone (Bangkok is not in Canada), and then using the new button to fix it

recording_20240817-184943.webm