feat: add distribution and fleet management — CI/CD, OCI, metrics, ARM64 (Phase 5)

- Gitea Actions CI pipeline: Go tests, build, shellcheck on push/PR
- Gitea Actions release pipeline: full build + artifact upload on version tags
- OCI container image builder for registry-based OS distribution
- Zero-dependency Prometheus metrics endpoint (kubesolo_os_info, boot,
  memory, update status) with 10 tests
- USB provisioning tool for air-gapped deployments with cloud-init injection
- ARM64 cross-compilation support (TARGET_ARCH env var + build-cross.sh)
- Updated build scripts to accept TARGET_ARCH for both amd64 and arm64
- New Makefile targets: oci-image, build-cross

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/release.yaml

@@ -0,0 +1,165 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+
+      - name: Test cloud-init
+        run: cd cloud-init && go test ./... -count=1
+
+      - name: Test update agent
+        run: cd update && go test ./... -count=1
+
+  build-binaries:
+    name: Build Binaries
+    runs-on: ubuntu-latest
+    needs: test
+    strategy:
+      matrix:
+        include:
+          - goos: linux
+            goarch: amd64
+            suffix: linux-amd64
+          - goos: linux
+            goarch: arm64
+            suffix: linux-arm64
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+
+      - name: Get version
+        id: version
+        run: echo "version=${GITHUB_REF#refs/tags/v}" >> $GITHUB_OUTPUT
+
+      - name: Build cloud-init
+        run: |
+          CGO_ENABLED=0 GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }} \
+            go build -ldflags="-s -w -X main.version=${{ steps.version.outputs.version }}" \
+            -o kubesolo-cloudinit-${{ matrix.suffix }} ./cmd/
+        working-directory: cloud-init
+
+      - name: Build update agent
+        run: |
+          CGO_ENABLED=0 GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }} \
+            go build -ldflags="-s -w -X main.version=${{ steps.version.outputs.version }}" \
+            -o kubesolo-update-${{ matrix.suffix }} .
+        working-directory: update
+
+      - name: Upload binaries
+        uses: actions/upload-artifact@v4
+        with:
+          name: binaries-${{ matrix.suffix }}
+          path: |
+            cloud-init/kubesolo-cloudinit-${{ matrix.suffix }}
+            update/kubesolo-update-${{ matrix.suffix }}
+
+  build-iso:
+    name: Build ISO (amd64)
+    runs-on: ubuntu-latest
+    needs: build-binaries
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.22'
+
+      - name: Install build deps
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            cpio gzip genisoimage isolinux syslinux syslinux-common \
+            syslinux-utils xorriso xz-utils wget squashfs-tools \
+            dosfstools e2fsprogs fdisk parted bsdtar
+
+      - name: Build ISO
+        run: make iso
+
+      - name: Build disk image
+        run: make disk-image
+
+      - name: Get version
+        id: version
+        run: echo "version=$(cat VERSION)" >> $GITHUB_OUTPUT
+
+      - name: Upload ISO
+        uses: actions/upload-artifact@v4
+        with:
+          name: iso-amd64
+          path: output/*.iso
+
+      - name: Upload disk image
+        uses: actions/upload-artifact@v4
+        with:
+          name: disk-image-amd64
+          path: output/*.img
+
+  release:
+    name: Create Release
+    runs-on: ubuntu-latest
+    needs: [build-binaries, build-iso]
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Get version
+        id: version
+        run: echo "version=$(cat VERSION)" >> $GITHUB_OUTPUT
+
+      - name: Download all artifacts
+        uses: actions/download-artifact@v4
+        with:
+          path: artifacts
+
+      - name: Compute checksums
+        run: |
+          cd artifacts
+          find . -type f \( -name "*.iso" -o -name "*.img" -o -name "kubesolo-*" \) \
+            -exec sha256sum {} \; | sort > ../SHA256SUMS
+          cd ..
+
+      - name: Create release
+        uses: softprops/action-gh-release@v2
+        with:
+          name: KubeSolo OS v${{ steps.version.outputs.version }}
+          body: |
+            ## KubeSolo OS v${{ steps.version.outputs.version }}
+
+            ### Downloads
+            - **ISO** — Boot from CD/USB, ideal for testing
+            - **Disk Image** — Raw disk with A/B partitions + GRUB
+            - **Binaries** — Standalone cloud-init and update agent
+
+            ### Verify
+            ```
+            sha256sum -c SHA256SUMS
+            ```
+
+            ### Quick Start
+            ```bash
+            # Boot in QEMU
+            qemu-system-x86_64 -m 1024 -smp 2 -enable-kvm \
+              -cdrom kubesolo-os-${{ steps.version.outputs.version }}.iso \
+              -nographic
+            ```
+          files: |
+            artifacts/**/*.iso
+            artifacts/**/*.img
+            artifacts/**/kubesolo-*
+            SHA256SUMS
+          draft: false
+          prerelease: false