Add ED25519 SSH key algorithm support to CLI

[deamwork]

Problem

The Infisical backend server supports issuing SSH credentials with ED25519 key algorithm, but the CLI cannot utilize this feature because:

1. The underlying go-sdk doesn't define the ED25519 constant
2. The CLI's algoToFileName map doesn't have an ED25519 mapping
3. The error message tells users that valid values are only: RSA_2048, RSA_4096, EC_prime256v1, EC_secp384r1

This prevents users from accessing the modern ED25519 key type via the CLI, even though the backend supports it.

Root Cause

The CLI inherits its limitations from the go-sdk. The go-sdk needs to add ED25519 support first, then the CLI must:

1. Update the algoToFileName map to include ED25519
2. Update the error message validation text

ref: Infisical/go-sdk#77

Evidence

Backend supports ED25519 as default:
https://github.com/Infisical/infisical/blob/fc5d42baf0259fd205f5ba8ae69a667c3406c40a/backend/src/ee/routes/v1/ssh-certificate-router.ts#L117

CLI missing ED25519 mapping:
https://github.com/Infisical/cli/blob/main/packages/cmd/ssh.go#L65-L70

var algoToFileName = map[infisicalSdkUtil.CertKeyAlgorithm]string{
	infisicalSdkUtil.RSA2048:   "id_rsa_2048",
	infisicalSdkUtil.RSA4096:   "id_rsa_4096",
	infisicalSdkUtil.ECDSAP256: "id_ecdsa_p256",
	infisicalSdkUtil.ECDSAP384: "id_ecdsa_p384",
	// Missing: ED25519
}

Error message needs update:
https://github.com/Infisical/cli/blob/main/packages/cmd/ssh.go#L221-L224

util.HandleError(fmt.Errorf("invalid keyAlgorithm: %s", keyAlgorithm),
	"Valid values: RSA_2048, RSA_4096, EC_prime256v1, EC_secp384r1")

Possible solution

1. Wait for go-sdk PR to merge (adds ED25519 constant)
2. Update algoToFileName map in cli/packages/cmd/ssh.go to include ED25519:

   var algoToFileName = map[infisicalSdkUtil.CertKeyAlgorithm]string{
       infisicalSdkUtil.RSA2048:   "id_rsa_2048",
       infisicalSdkUtil.RSA4096:   "id_rsa_4096",
       infisicalSdkUtil.ECDSAP256: "id_ecdsa_p256",
       infisicalSdkUtil.ECDSAP384: "id_ecdsa_p384",
       infisicalSdkUtil.ED25519:   "id_ed25519",
   }

3. Update the error message to include ED25519

Expected Behavior

Users should be able to run:

infisical ssh issue-credentials \
  --certificateTemplateId <template-id> \
  --principals <username> \
  --keyAlgorithm ED25519 \
  --outFilePath ~/.ssh/

And successfully receive ED25519-based SSH credentials.

• algoToFileName map includes ED25519 → "id_ed25519" mapping
• Error validation message includes ED25519 as a valid option
• CLI can issue SSH credentials with ED25519 key algorithm
• Generated key file is named id_ed25519
• Change is backward compatible