Explore new `temporal_rs` crate for date/timezone localization

[kevinaboos]

The first "stable" release of temporal_rs has recently been made available: https://boajs.dev/blog/2025/09/24/temporal-release

crates.io link: https://crates.io/crates/temporal_rs

There are few TODO items scattered across Robrix related to
For example, here is one in the Timestamp widget:

robrix/src/shared/timestamp.rs

Lines 59 to 60 in 3fa173e

	// TODO: use pure_rust_locales crate to format the time based on the chosen Locale.
	let locale_extended_fmt_en_us= "%a %b %-d, %Y, %r";

and here's the same example duplicated in the EditedIndicator widget:

robrix/src/home/edited_indicator.rs

Lines 77 to 78 in 3fa173e

	// TODO: use pure_rust_locales crate to format the time based on the chosen Locale.
	let locale_extended_fmt_en_us= "%a %b %-d, %Y, %r";

I'm not sure if temporal_rs will help make this easier, or if it's too big to be worth the compilation time costs, but we should investigate it nonetheless.