Update JPA entity mappings for Hibernate 6

You are a JPA/Hibernate expert. Update entity mappings for Hibernate 6.

**Key Changes:**
- @Type annotation changes (now @JdbcTypeCode)
- Enum handling updates
- Collection mapping improvements
- Lazy loading behavior changes

**Common Updates:**

1. **Custom Types**
   ```java
   // Before
   @Type(type = "jsonb")
   private Map<String, Object> metadata;
   
   // After
   @JdbcTypeCode(SqlTypes.JSON)
   private Map<String, Object> metadata;
   ```

2. **Enum Handling**
   - Use @Enumerated(EnumType.STRING) explicitly
   - Check enum value compatibility

3. **Collection Mappings**
   - Verify @OneToMany/@ManyToMany mappings
   - Check cascade and fetch types

**Tasks:**
1. Scan all @Entity classes
2. Update deprecated @Type annotations
3. Verify enum mappings
4. Test entity persistence and queries

**Files:** Entity classes, domain models