Add AdvancedSearch support for filtering mails before a given date

[codiflow]

The current implementation of AdvancedSearch only allows filtering of emails which arrived since a given date. As one can easily modify the search string (which for example is since=2024-05-27) to also filter mails which have arrived until a given date we should also add this functionality to the drop down as well to make it easier for users to access this option.

There are some small things to consider before merging this:

1. Currently { id: -1, name: i18n(prefix + 'ALL') }, filters for all mails. Maybe it would be better to switch to 0 here instead of -1 to have it designed more intuitively like all positive numbers are searches before a given date and all negative numbers are searches until a given date.
2. The language strings have no prefix (yet) which differentiates between since and before. We should add that (see my comment in the code before let prefix = 'SEARCH/DATE_';)
3. The corresponding language strings are missing yet because I couldn't find the respective files – would be glad if you could tell me where to find them.
4. The code has not been tested yet because I've no dev setup in place currently.

[the-djmaze]

The translations can be found here:

snappymail/snappymail/v/0.0.0/app/localization/en/user.json

Lines 61 to 67 in 55b8620

	"DATE_ALL": "All",
	"DATE_3_DAYS": "Up to 3 days old",
	"DATE_7_DAYS": "Up to 1 week old",
	"DATE_MONTH": "Up to 1 month old",
	"DATE_3_MONTHS": "Up to 3 months old",
	"DATE_6_MONTHS": "Up to 6 months old",
	"DATE_YEAR": "Up to 1 year old",

[codiflow]

Thank you for merging this – I did not have the time yet to adapt the lanugage strings. Thank you for doing that for me 🙏

[the-djmaze]

It's not merged. But i will add your changes