Consider using HTMX instead of React

[php-coder]

We should evaluate HTMX (https://htmx.org) and if it's good, let's use it instead of React (see #1328), our own jQuery code (see also #1211) and axios (#1497).

Useful links:

• [x] https://www.dev-notes.ru/articles/javascript/htmx-introduction/ 🇷🇺 (htmx-indicator might be useful)
• [x] https://htmx.org/extensions/loading-states/ data-loading-disable
• [x] https://htmx.org/extensions/json-enc/ json-enc
• [x] https://htmx.org/extensions/response-targets/
• [x] https://htmx.org/extensions/include-vals/
• [x] https://htmx.org/extensions/client-side-templates/
• [ ] https://dev.to/yosephtenaw/use-htmx-with-spring-boot-and-thymeleaf-18g9 (pinboard)