Package more optional KDE dependencies

[rxrbln]

Package more optional KDE dependencies

[JeremyZeng77]

I am working on a focused first pass here: wiring currently missing optional KDE dependency toggles so builds degrade gracefully when optional libs are absent. I am starting with K3b, where upstream exposes dedicated CMake switches for docs, DVD ripping, Taglib and FFmpeg decoder plugins.

[JeremyZeng77]

Opened a focused first-pass PR for this: #409. It wires K3b's upstream optional feature switches to T2 pkginstalled guards so the package degrades more gracefully on leaner builds.

[JeremyZeng77]

Extended the first-pass PR further: it now also adds Kaffeine optional dependency metadata for docs and DVB support paths, following upstream's optional feature handling.

[JeremyZeng77]

Extended PR #409 again with another pass of optional KDE metadata:\n\n- okular: marked the optional document backends and integrations already handled via FORCE_NOT_REQUIRED_DEPENDENCIES guards\n- alkon: marked optional Python support via pyside6\n- kimageformats: marked optional JPEG2000 support via openjpeg\n\nValidation on this pass: scripts/Check-PkgFormat okular, scripts/Check-PkgFormat falkon, scripts/Check-PkgFormat kimageformats, and git diff --check.