scaffold: aports overlay, build script, CI workflow, README

Kernel aport forked from pmaports 7.1.2-r0, repointed at milos-linux
combined-stable with the tested FP6 config (+EFI_ZBOOT for packaging);
imsd + nftables aports from the pending pmaports submission. build.sh
carries TODO(validate) markers - not yet run end-to-end.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

aports/modem/imsd/APKBUILD

@@ -0,0 +1,48 @@
+maintainer="Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>"
+pkgname=imsd
+pkgver=0.3.0
+pkgrel=0
+pkgdesc="Userspace IMS/VoLTE daemon for mainline Linux phones"
+url="https://forgejo.catcrafts.net/Catcrafts/imsd"
+# other arches: nothing wrong known, just never run there
+arch="aarch64 x86_64"
+license="GPL-3.0-only"
+# the media leg dlopen's the AMR-WB codecs; pw-record/pw-play drive PipeWire —
+# none of which abuild's .so auto-scan can see
+depends="modemmanager opencore-amr vo-amrwbenc pipewire-tools"
+# clang/libc++ C++26-modules build (upstream Makefile); llvm-runtimes ships
+# the libc++ std module sources the build precompiles
+makedepends="clang lld libc++-dev llvm-libunwind-dev llvm-runtimes glib-dev pkgconf"
+# the versioned provides both satisfies soc-qcom-modem's 81voltd dependency
+# and excludes the real package: 81voltd serves the modem firmware's own
+# ims-PDN requests, which races imsd for the PDN and flaps it (a new prefix
+# every ~2.5 min) — two IMS stacks cannot share one PDN. Installing imsd is
+# an explicit choice to hand the IMS PDN to userspace.
+provides="81voltd=$pkgver-r$pkgrel"
+# no OpenRC service yet: the unit's PDN-bring-up/env-file sequencing is only
+# tested under systemd; an initd is welcome once someone can verify one
+subpackages="$pkgname-systemd"
+source="$pkgname-$pkgver.tar.gz::$url/archive/v$pkgver.tar.gz"
+builddir="$srcdir/$pkgname"
+
+build() {
+	make
+}
+
+check() {
+	make check
+}
+
+package() {
+	make install DESTDIR="$pkgdir"
+}
+
+systemd() {
+	install_if="$pkgname=$pkgver-r$pkgrel systemd"
+
+	amove usr/lib/systemd/system
+}
+
+sha512sums="
+PLACEHOLDER_RUN_PMBOOTSTRAP_CHECKSUM_AFTER_V0_3_0_TAG_EXISTS  imsd-0.3.0.tar.gz
+"