This release upgrades the project to Spring Boot 4.0.0 and Java 25, migrates all entity primary keys from sequential Long to UUID, and improves the base module architecture by centralizing the @Id field in BaseEntity.

All entity IDs have been migrated from Long to java.util.UUID.

• REST API endpoints now expect and return UUIDs instead of numeric IDs (e.g., /users/550e8400-e29b-41d4-a716-446655440001instead of /users/123)
• Database columns are now UUID type instead of BIGINT. Existing databases require manual data migration.
• JSON payloads represent IDs as strings (Jackson handles UUID serialization/deserialization automatically)

The @Id field with @GeneratedValue and @UuidGenerator is now defined once in BaseEntity. Subclass entities (User, TokenEntity) no longer declare their own ID field or sequence generators.

Upgraded from Spring Boot 3.2.3 / Java 21 to Spring Boot 4.0.0 / Java 25.

If you have an existing database with BIGINT primary keys, you'll need to run a migration:

-- Example for PostgreSQL

ALTER TABLE _user ALTER COLUMN id TYPE UUID USING gen_random_uuid();

ALTER TABLE token ALTER COLUMN id TYPE UUID USING gen_random_uuid();

ALTER TABLE token ALTER COLUMN user_id TYPE UUID;

Warning: This will generate new UUIDs, breaking any externally stored references to old numeric IDs. Plan accordingly.

• Update all client code to send/receive UUID strings instead of numeric IDs
• URL patterns change from /users/123 to /users/550e8400-e29b-41d4-a716-446655440001

• All 24 tests pass (mvn test — 12 core + 12 API)
• Clean compilation with no warnings (mvn clean compile)