RaDiaTech UI additions for SFTPGo Community Edition 2.7.6 / commit 62ae9ba3

Upstream: https://github.com/drakkan/sftpgo/tree/v2.7.6
Full upstream source: https://github.com/drakkan/sftpgo/archive/refs/tags/v2.7.6.zip
This archive contains modified Go HTML templates, Russian i18next messages, a CSS overlay and the pinned Flatpickr locale.
SFTPGo templates and their modifications: GNU AGPL v3; see licenses/SFTPGo-LICENSE.txt and SFTPGo-NOTICE.txt.
Flatpickr 4.6.13: MIT; see licenses/Flatpickr-LICENSE.txt.
The proprietary RaDiaTech trademark artwork is not licensed as software and is not included here.

Install: use the matching upstream templates directory as the base, overlay templates/, put locales/ru/translation.json in the static locales directory and flatpickr/l10n/ru.js in assets/plugins/custom/flatpickr/l10n/. Serve branding/ through the configured branding alias. Enable [ru,en] on the HTTP bindings, set logo_path to the authorized artwork, extra_css to /branding/exchange-rdt-ru1.css, and remove disclaimer name/path. Use a separate versioned template directory and restart SFTPGo after validating the templates. Bindings/templates are loaded at startup, not SIGHUP. Preserve original service permissions and auth settings.

Release: rdt-ui-20260927-limits-v1. Includes updated share form and the separate SQLite policy DDL. Apply the DDL only to a reviewed compatible SFTPGo 2.7.6 SQLite provider; after schema migration/restore verify both owned persistent triggers. UI validation alone is not enforcement.
