fix(ci): correct ARM64 architecture naming in Arch workflow

- Fix PROTOC_ARCH_NAME: aarch_64 → aarch64 (matches protobuf releases)
- Fix PKGBUILD arch field: use ${ARCH} variable instead of hardcoded 'x86_64'
- Ensures ARM64 builds will work when re-enabled

Addresses CodeRabbit findings

Author: PythonTilk

.github/workflows/linux_packages_arch.yaml

@@ -166,7 +166,7 @@ jobs:
           pkgver=${VERSION}
           pkgrel=1
           pkgdesc="AI-powered note-taking and transcription application"
-          arch=('x86_64')
+          arch=("${ARCH}")
           url="https://github.com/different-ai/hyprnote"
           license=('custom')
           depends=(
@@ -238,7 +238,7 @@ jobs:
           if [[ "${{ matrix.arch }}" == "x86_64" ]]; then
             PROTOC_ARCH_NAME="x86_64"
           else
-            PROTOC_ARCH_NAME="aarch_64"
+            PROTOC_ARCH_NAME="aarch64"
           fi
           
           # Run build in Docker container with appropriate platform