JUCE_USE_CURL defaults to 1 on Linux, so juce_core compiled
juce_Network_curl.cpp and included <curl/curl.h>. Nothing linked libcurl
(NEEDS_CURL was off), but its development headers were still a hard build
requirement. Set JUCE_USE_CURL=0 and pin NEEDS_CURL/NEEDS_WEB_BROWSER to
FALSE alongside the existing JUCE_WEB_BROWSER=0.
X11's Xrandr/Xinerama/Xshm/Xcursor headers are only dlsym()ed at runtime, but
live in separate -dev packages on Arch/Artix. Probe each with
check_include_file_cxx and define the JUCE_USE_* flags accordingly, so a
distro carrying just libX11 still builds.
Also check alsa/freetype2/fontconfig up front with a distro-specific hint
instead of letting JUCE's raw pkg-config error surface, and expand the
README's Linux section to cover all of it.
- Tune the live spectrum display to a fixed range matched to real per-FFT-bin
levels (-40..0 dB) so typical content sits mid-screen instead of flying to
the top or hugging the bottom; widen the SENS offset control to -48..+24 dB
- Disable JUCE_WEB_BROWSER so the WebKitGTK WebBrowserComponent (unused) is
compiled out, letting the plugin build on Artix/Arch without GTK/WebKit dev
headers
- Add a verbose README covering the bands, parameters, controls, structure,
DSP, build steps, and the Linux/Artix note
