* Add UI for advanced search
To help users with the seach operators.
Obviously not as powerful as a manually-written search query.
Lack in particular negation and logical *and* for now, but I might try to do something about it.
<img width="939" height="1438" alt="image" src="https://github.com/user-attachments/assets/0bcad39b-eff3-4f44-876b-a2552af2af00" />
* Consistency: allow multiple user queries like S:1,2
* Fix user query and add tests
* Change regional language codes
According to `ISO-639-1` and `ISO-3166-1 alpha-2` recommendations, regional
languages must be written with the language code in lowercase and the region
in uppercase. For instance, we should have `en-US` instead of `en-us`.
Folders have been updated to reflect those recommendations and regional
language codes have been updated in the translation files.
* Update README files
* Fix configuration for typos
* Revert language order in documentation
* Remove unnecessary code
* Change language configuration getter
* Fix phpstan error
* Fix typo
* Add types
* escape regex
* Move language logic to avoid magic or deprecated methods
* Minor fix on regex
