Add querydsl-ktx to Database subcategory

[HarryJhin]

Add querydsl-ktx to the Database subcategory.

querydsl-ktx provides null-safe infix Kotlin extensions for QueryDSL dynamic queries. It eliminates manual BooleanBuilder null checks by providing eight extension interfaces that turn if (x != null) builder.and(...) patterns into declarative infix expressions like entity.name eq name.

• Published on Maven Central: io.github.harryjhin:querydsl-ktx
• Spring Boot 3.0+, QueryDSL 5.1.0+, Kotlin 1.7+, JDK 17+
• Documentation