Allow Flyway CLI to target DB modifiers

[ar-agt]

Summary

• add an explicit Flyway target model so CLI/QBean callers can choose a DB config modifier independently from the Flyway history table
• stop the Flyway CLI prompt from instantiating DB/bootstrapping Hibernate just to enter the subsystem; Flyway now resolves JDBC properties directly
• support --db, --table, --prefix, and legacy positional DB modifiers, and document the tenant use cases

Validation

• ./gradlew :modules:db-flyway:test :modules:dbsupport:test
• ./gradlew :modules:db-flyway:check
• git diff --check
• ./gradlew check