feat: add cloud-init Go parser (Phase 2)

Implement a lightweight cloud-init system for first-boot configuration:
- Go parser for YAML config (hostname, network, KubeSolo settings)
- Static/DHCP network modes with DNS override
- KubeSolo extra flags and API server SAN configuration
- Portainer Edge Agent and air-gapped deployment support
- New init stage 45-cloud-init.sh runs before network/hostname stages
- Stages 50/60 skip gracefully when cloud-init has already applied
- Build script compiles static Linux/amd64 binary (~2.7 MB)
- 17 unit tests covering parsing, validation, and example files
- Full documentation at docs/cloud-init.md

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

build/scripts/build-cloudinit.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+# build-cloudinit.sh — Compile the cloud-init binary as a static Linux binary
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
+CACHE_DIR="${CACHE_DIR:-$PROJECT_ROOT/build/cache}"
+CLOUDINIT_SRC="$PROJECT_ROOT/cloud-init"
+
+OUTPUT="$CACHE_DIR/kubesolo-cloudinit"
+
+echo "==> Building cloud-init binary..."
+
+if ! command -v go >/dev/null 2>&1; then
+    echo "ERROR: Go is not installed. Install Go 1.22+ to build cloud-init."
+    echo "  https://go.dev/dl/"
+    exit 1
+fi
+
+mkdir -p "$CACHE_DIR"
+
+cd "$CLOUDINIT_SRC"
+
+# Run tests first
+echo "    Running tests..."
+go test ./... -count=1 || {
+    echo "ERROR: Tests failed. Fix tests before building."
+    exit 1
+}
+
+# Build static binary for Linux amd64
+echo "    Compiling (CGO_ENABLED=0 GOOS=linux GOARCH=amd64)..."
+CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build \
+    -ldflags='-s -w' \
+    -o "$OUTPUT" \
+    ./cmd/
+
+echo "    Built: $OUTPUT ($(du -h "$OUTPUT" | cut -f1))"
+echo ""

build/scripts/inject-kubesolo.sh

@@ -63,6 +63,16 @@ for lib in network.sh health.sh; do
     [ -f "$src" ] && cp "$src" "$ROOTFS/usr/lib/kubesolo-os/$lib"
 done
 
+# Cloud-init binary (Go, built separately)
+CLOUDINIT_BIN="$CACHE_DIR/kubesolo-cloudinit"
+if [ -f "$CLOUDINIT_BIN" ]; then
+    cp "$CLOUDINIT_BIN" "$ROOTFS/usr/lib/kubesolo-os/kubesolo-cloudinit"
+    chmod +x "$ROOTFS/usr/lib/kubesolo-os/kubesolo-cloudinit"
+    echo "    Installed cloud-init binary ($(du -h "$CLOUDINIT_BIN" | cut -f1))"
+else
+    echo "    WARN: Cloud-init binary not found (run 'make build-cloudinit' to build)"
+fi
+
 # --- 3. Kernel modules list ---
 cp "$PROJECT_ROOT/build/config/modules.list" "$ROOTFS/usr/lib/kubesolo-os/modules.list"