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/root.go

@@ -33,6 +33,7 @@ func init() {
 	rootCmd.AddCommand(scanCmd)
 	rootCmd.AddCommand(providersCmd)
 	rootCmd.AddCommand(configCmd)
+	rootCmd.AddCommand(legalCmd)
 	// Stub commands for future phases (per CLI-01 requirement of 11 commands)
 	rootCmd.AddCommand(verifyCmd)
 	rootCmd.AddCommand(importCmd)