fix(pollux): replace generic Error with domain-specific PolluxError/CastorError in JWT utils
Replaces 13 instances of generic `throw new Error()` with domain-specific error types (`PolluxError.InvalidCredentialError`, `CastorError.NotPossibleToResolveDID`, `CastorError.InvalidKeyError`) across the JWT/SDJWT utility layer. This enables callers to programmatically distinguish between error types (e.g., invalid DID document vs invalid key vs invalid credential), which is essential for the Identity Portal to display meaningful error messages. Files changed: - SDJWT.ts: 6 errors replaced - JWT.ts: 4 errors replaced - ResolveDID.ts: 1 error replaced - CreateJwt.ts: 1 error replaced - CreateSDJWT.ts: 1 error replaced - Added tests for error type verification Signed-off-by: Abhigyan Singh <[email protected]>