feat: Add multi-day share

[vdrumsta]

Context

Currently there is an ability to share a single day entry. I was looking to share multiple days.

For my use case, I only needed to share text, but if there's a need, I'd be happy to update the code to share images too. Maybe with an option presented whether to share with images or text only. Not sure what's the ideal UX here.

[Demizo]

This is awesome! I applaud you for putting up with my horrible codebase 😜

Maybe with an option presented whether to share with images or text only. Not sure what's the ideal UX here.

There could be a popup when sharing multiple entries with a toggle for images, but that seems like it could be annoying. I would be in favor of defaulting to always sharing images. The rationale being that the user could remove the images after the fact if they really wanted/needed to. For example, when sharing to a messaging or email app.

Some thoughts:

• Would it make sense to move this selection functionality to the gallery page? That way the user could easily filter down to specific entries if desired. We could even provide a select all button in this case. For example, if one wants to show a friend every entry containing that friend's name. (We would want to hide the search bar in selection mode since that is a world of edge cases I don't want to think about).
• I am by no means an expert in Flutter best practices, but it seems like we could avoid the extra provider. Since the selection is local to the current page, it could be managed within that page's state. If the feature is moved to the gallery page, this would be trivial since the gallery already manages the gesture detectors for entries. On the home page, the entry day cells would need to provide a callback to indicate when they are selected.
• The "selected" count text should be a localized string, but I could do this after the fact as well.