Move the .ini language files from src/resources/langs/ to
src/Core/Localization/lang/, next to the Translator subsystem that owns
them — which already defaulted its $langsDir to __DIR__ . '/lang/'. This
dissolves the now-vestigial src/resources/ bucket (its data/ tree went
with admin_constants, libs/ was empty).
- bootstrap.php calls Translator::init() with no argument, relying on the
class's own __DIR__-relative default instead of MAIN_HOME . 'resources/langs/'.
- Makefile LB removal list points at Core/Localization/lang (and drops the
gone resources/langs, resources/libs); LB still ships no UI translations.
- Drop the stale src/resources entries from phpstan scanDirectories and the
phpunit coverage excludes.
- Update the English docs (translations guide, build-system table); the ru
tree is regenerated before release.
- add PHPUnit bootstrap and config under tests/
- add focused unit tests for GitHubReleases, InputValidator and FfmpegPaths
- fix GitHubReleases cache file handling when switching update channel
- document PHPUnit PHAR usage and debug run commands in RU/EN docs
- document SFTP sync for tests/ and contributor test workflow
- remove broad smoke coverage approach in favor of per-file tests