fix(annotations): Ensure timezone alignment

[Twixes]

Problem

Some annotations near period edges fell into the neighbor period because of timezone mismatches (unless both the project and client were set to UTC).

Changes

All annotations should now be bucketed accurately.

How did you test this code?

Updated logic tests to verify timezone correctness too.

[benjackwhite]

@Twixes additional context - Added to a chart with "day" interval. They don't show up after adding or refresh but do show up when grouped by week/month

[Twixes]

Hmm, I suspect it was because of the insight timezone being out sync with the project timezone. Or at least I can't reproduce this anymore. Can you try now?

[pauldambra]

something is off somewhere :)

[Twixes]

Should be good now, can you take a second look? @benjackwhite @pauldambra

[pauldambra]

grouped by day it seems to be off by a day?

I started from scratch on fresh install, viewed weekly active users and added some annotations, and then shifted to group by day. set to UTC

[pauldambra]

Although it's actually worse in Master 🤣 So no reason to block this PR

[Twixes]

Thanks for letting me know, all the cases seem to work as expected now!