Restored original license signing key from backup - key was never
compromised (private repo). Removes unnecessary dual-key complexity:
- Remove legacyPublicKey and SetLegacyPublicKey from license.go
- Simplify signature verification to single key
- Remove EmbeddedLegacyPublicKey from pubkey.go
- Remove PULSE_LICENSE_LEGACY_PUBLIC_KEY from Dockerfile and workflows
- Remove dual-key test
- Simplify mock.env