Fix non-portable BLOB columnDefinition in WebAuthnCredential (#275)

* fix: Remove non-portable BLOB columnDefinition from WebAuthnCredential

Remove hardcoded `columnDefinition = "BLOB"` from three byte[] fields
in WebAuthnCredential. The `@Lob` annotation already handles dialect-
appropriate type mapping (BLOB for MySQL, bytea for PostgreSQL, etc.).
The explicit columnDefinition bypassed Hibernate's dialect translation,
causing DDL failures on PostgreSQL and other non-MySQL databases.

Fixes #274

* fix: Use plain byte[] instead of @lob for portable WebAuthn columns

Replace `@Lob @column(columnDefinition = "BLOB")` with plain `byte[]`
and explicit `@Column(length = ...)` on the three binary fields in
WebAuthnCredential.

`@Lob` on byte[] in Hibernate 7 generates literal `blob` in DDL,
which bypasses dialect translation and fails on PostgreSQL (no `blob`
type). Plain byte[] lets each dialect choose the correct native type:
`bytea` on PostgreSQL, `varbinary`/`mediumblob` on MySQL.

Verified DDL generation against a real PostgreSQL 16 instance and
confirmed all three columns map to `bytea`. Full H2 test suite passes
with no regressions.

Fixes #274

Author: devondragon

src/main/java/com/digitalsanctuary/spring/user/persistence/model/WebAuthnCredential.java

@@ -6,7 +6,6 @@
 import jakarta.persistence.FetchType;
 import jakarta.persistence.Id;
 import jakarta.persistence.JoinColumn;
-import jakarta.persistence.Lob;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.Table;
 import lombok.Data;
@@ -31,8 +30,7 @@ public class WebAuthnCredential {
 	private WebAuthnUserEntity userEntity;
 
 	/** COSE-encoded public key (typically 77-300 bytes, RSA keys can be larger). */
-	@Lob
-	@Column(name = "public_key", nullable = false, columnDefinition = "BLOB")
+	@Column(name = "public_key", nullable = false, length = 2048)
 	private byte[] publicKey;
 
 	/** Counter to detect cloned authenticators. */
@@ -60,13 +58,11 @@ public class WebAuthnCredential {
 	private boolean backupState;
 
 	/** Attestation data from registration (can be several KB). */
-	@Lob
-	@Column(name = "attestation_object", columnDefinition = "BLOB")
+	@Column(name = "attestation_object", length = 65536)
 	private byte[] attestationObject;
 
 	/** Client data JSON from registration (can be several KB). */
-	@Lob
-	@Column(name = "attestation_client_data_json", columnDefinition = "BLOB")
+	@Column(name = "attestation_client_data_json", length = 65536)
 	private byte[] attestationClientDataJson;
 
 	/** Creation timestamp. */