feat(05-02): add LEGAL.md, embed it, and wire keyhunter legal command

- Add LEGAL.md at repo root (109 lines) covering CFAA, Computer Misuse Act,
  EU Directive 2013/40/EU, responsible use, disclosure, and disclaimer.
- Mirror to pkg/legal/LEGAL.md for go:embed (Go cannot traverse parents).
- Add pkg/legal package exposing Text() for the embedded markdown.
- Add cmd/legal.go registering keyhunter legal subcommand to print it.

cmd/legal.go

@@ -0,0 +1,17 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/salvacybersec/keyhunter/pkg/legal"
+	"github.com/spf13/cobra"
+)
+
+var legalCmd = &cobra.Command{
+	Use:   "legal",
+	Short: "Print the legal disclaimer for the --verify feature",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		fmt.Println(legal.Text())
+		return nil
+	},
+}