firefox-fourier: ship .desktop launcher (pkgrel=7)

Stock firefox.desktop disappears when our 'provides=firefox' replaces stock
firefox-arch, so installing firefox-fourier left the user without a Plasma/GNOME
start-menu entry. Add firefox-fourier.desktop with Categories=Network;WebBrowser;
(routes under Internet on KDE Plasma 6), MIME types for the usual web schemes,
new-window / private-window actions, and the 128px icon from the package's
internal browser/chrome/icons tree.

Reported on ohm (PineTab2 / Plasma 6) — manual /usr/share/applications shim
proved the file works; this commits it to the recipe so future installs Just Work.

arch/firefox-fourier/PKGBUILD

@@ -13,7 +13,7 @@
 
 pkgname=firefox-fourier
 pkgver=150.0.1
-pkgrel=6
+pkgrel=7
 pkgdesc='Firefox with V4L2 stateless HW video decode unlocked for mainline Linux Rockchip'
 arch=('aarch64' 'x86_64')
 url='https://www.mozilla.org/firefox'
@@ -91,8 +91,11 @@ source=(
   # Vendor-default prefs that gate the patched VAAPI path on RK3399 —
   # widget.dmabuf.force-enabled etc. See marfrit-packages#8 for evidence.
   'rockchip-fourier-defaults.js'
+  # Plasma/GNOME start-menu entry — categorises under Internet, picks the
+  # 128px firefox icon shipped under /usr/lib/firefox-fourier/browser/.
+  'firefox-fourier.desktop'
 )
-sha256sums=('SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP')
+sha256sums=('SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP' 'SKIP')
 
 prepare() {
   cd "${srcdir}/firefox-${pkgver}"
@@ -180,4 +183,11 @@ LAUNCHER
   # VAAPI_VLD` + dmabuf surfaces locking end-to-end.
   install -Dm644 "${srcdir}/rockchip-fourier-defaults.js" \
     "${pkgdir}/usr/lib/firefox-fourier/defaults/preferences/rockchip-fourier-defaults.js"
+
+  # Desktop entry — fileless install would leave the package without a
+  # start-menu entry (stock firefox.desktop disappears when our `provides`
+  # replaces stock firefox). Plasma & GNOME pick this up via the
+  # `Categories=Network;WebBrowser;` line → "Internet" submenu.
+  install -Dm644 "${srcdir}/firefox-fourier.desktop" \
+    "${pkgdir}/usr/share/applications/firefox-fourier.desktop"
 }