fix: PKGBUILD compatibility with numa v0.10.1, fix QEMU action SHA pin

Three small bug fixes that make this PR mergeable end-to-end against
current main, without changing the package design (still numa-git,
still pushed on every main commit, still tracking HEAD via pkgver()):

1. Simplified prepare() — drop the obsolete sed patching for
   /usr/local/bin/numa. That literal only appears in a comment
   in current main; the actual binary path is determined at
   runtime via std::env::current_exe(). Additionally, numa
   v0.10.1 ships PR #43 which makes numa FHS-compliant on Linux
   out of the box (/var/lib/numa for data dir), so no source
   patching is needed at all on Arch.

2. Fixed package() sed for the systemd unit. The previous sed
   targeted "ExecStart=/usr/local/bin/numa" but numa.service
   actually uses "{{exe_path}}" as a templating placeholder
   that's substituted at runtime by replace_exe_path() when
   `numa install` runs. The sed silently did nothing, and the
   AUR-installed unit file would have a literal "{{exe_path}}"
   that systemd cannot start. Fixed sed:

     sed 's|{{exe_path}}|/usr/bin/numa /etc/numa.toml|g' \
       numa.service > numa.service.patched

3. Fixed broken docker/setup-qemu-action SHA pin in
   publish-aur.yml. The pinned SHA
   6882732593b27c7f95a044d559b586a46371a68e doesn't exist as
   a commit in upstream docker/setup-qemu-action. Verified
   v3.0.0 SHA is 68827325e0b33c7199eb31dd4e31fbe9023e06e3.
   Without this fix the aarch64 validate job would fail to
   load the action at workflow start.

Also refreshed the stale pkgver placeholder in PKGBUILD and
.SRCINFO from 0.9.1.r0.g1234abc to 0.10.1.r0.g0000000 — purely
cosmetic since pkgver() auto-overrides on every makepkg run,
but at least the in-VC value reflects the current era.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = numa-git
 	pkgdesc = Portable DNS resolver in Rust — .numa local domains, ad blocking, developer overrides, DNS-over-HTTPS
-	pkgver = 0.9.1.r0.g1234abc
+	pkgver = 0.10.1.r0.g0000000
 	pkgrel = 1
 	url = https://github.com/razvandimescu/numa
 	arch = x86_64