fix(builder): truncate large error output to prevent log overflow

Build errors from nix can be very large (100k+ chars). This truncates
error output to the first 50 and last 50 lines when it exceeds 100
lines, preventing journal and NATS message overflow.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/homelab-deploy/main.go

@@ -17,7 +17,7 @@ import (
 	"github.com/urfave/cli/v3"
 )
 
-const version = "0.2.0"
+const version = "0.2.1"
 
 func main() {
 	app := &cli.Command{