feat: search/filter on https://sofka.rs/plugins

[vyrti]

web catalog is amazing idea
BUT currently its hard to check whats available and what those plugins actually do

[vyrti]

@nklmilojevic
also one bug:
https://sofka.rs/plugins
does not have full header, some points missing, so navigation is broken on site
8 on main site and 5 on plugins page

[nklmilojevic]

Agreed: add browser-side catalog search over existing plugin and command information, with clear results and useful descriptions. The reported missing header links need a separate bug check so the search change stays focused.

Implementation scope and acceptance checks: #646