feat: add structured logging, --dev flag, and snapshot network_overrides

- Add --dev flag to main that enables logrus caller info (file:line) for
  easier debugging without changing production log output
- Wire firecracker SDK logger (WithLogger) and FIFO log file to both the
  golden VM and each clone machine so Firecracker's own logs are surfaced
- Log the exact shell commands being run (cp --reflink, ip tuntap, ip link,
  firecracker binary) at Info level before each syscall/exec, making it
  straightforward to reproduce steps manually
- Extract snapshot.go with loadSnapshotWithNetworkOverride: a direct PUT
  /snapshot/load call over the Unix socket that includes network_overrides,
  remapping the stored tap to the per-clone tap name (Firecracker v1.15+
  feature not yet exposed by SDK v1.0.0)
- Use firecracker.WithSnapshot + a Handlers.FcInit.Swap to replace the SDK's
  LoadSnapshotHandler with the above when Bridge != "none"

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

main.go

@@ -18,11 +18,36 @@ package main
 import (
 	"fmt"
 	"os"
+	"path/filepath"
+	"runtime"
+
+	log "github.com/sirupsen/logrus"
 
 	"github.com/kacerr/fc-orchestrator/orchestrator"
 )
 
 func main() {
+	// strip --dev flag before subcommand routing
+	dev := false
+	filtered := os.Args[:1]
+	for _, a := range os.Args[1:] {
+		if a == "--dev" {
+			dev = true
+		} else {
+			filtered = append(filtered, a)
+		}
+	}
+	os.Args = filtered
+
+	if dev {
+		log.SetReportCaller(true)
+		log.SetFormatter(&log.TextFormatter{
+			CallerPrettyfier: func(f *runtime.Frame) (string, string) {
+				return "", fmt.Sprintf("%s:%d", filepath.Base(f.File), f.Line)
+			},
+		})
+	}
+
 	// figure out if we are running as root
 	if os.Geteuid() == 0 {
 		fmt.Println("Running with root/sudo privileges!")
@@ -61,7 +86,10 @@ func main() {
 }
 
 func usage() {
-	fmt.Fprintf(os.Stderr, `Usage: %s <command> [args]
+	fmt.Fprintf(os.Stderr, `Usage: %s [--dev] <command> [args]
+
+Flags:
+  --dev         log format with source file:line (e.g. file="orchestrator.go:123")
 
 Commands:
   init          Download kernel + create Alpine rootfs