Upgrade jOOQ 3.20.11 → 3.21.6

Adopt the jOOQ 3.21 line, bumping version.org.jooq in the root pom.xml (line 33) from 3.20.11 to 3.21.6. In jOOQ’s release cadence a minor bump (3.20 → 3.21) is the effective major boundary: it is where deprecated API is removed and code-generation output shape can change, so it is worth treating as a real upgrade even though the version delta looks small. 3.21 keeps the JDK-21 runtime floor 3.20 already established, so the "generated output targets Java 17" contract is undisturbed (the sakila-example module, which compiles generated code at --release 17, is the guard).

A full-pipeline dry run (mvn install -Plocal-db) with 3.21.6 came back completely clean: all four jOOQ artifacts (jooq, jooq-meta, jooq-codegen, jooq-codegen-maven) resolved, all 13 modules built, all tests passed, and the three risk areas all held: the graphitron-sakila-db codegen (with our custom NodeIdFixtureGenerator strategy, OrgCodeStringConverter forcedType, and the stock-JavaGenerator execution), the generator’s own JooqCatalog meta-model reflection, and the generated-code compile + DB execution in sakila-example. None of the 3.21 deprecations from the release notes (DataType.isQualifiedRecord, Internal.createParameter, XML-formatting methods, the retired INGRES/ORACLE10G dialects) touch our surface. So this is expected to be a one-line version bump with no code changes, confirming the single-version-lockstep strategy: the emitted jOOQ surface is all stable core org.jooq API, and the pipeline verifies the parts that are not compile-checked in the generator.

One process note for the implementer: switching jOOQ versions leaves stale jOOQ-generated sources under graphitron-sakila-db/target/generated-sources/jooq/. During the research a bump followed by a revert produced spurious org.jooq.impl.Internal.condition(…​) / TableLike cannot-convert errors because 3.21-shaped generated code met a reverted 3.20 runtime; a mvn clean before rebuilding avoids it. Independent of the graphql-java items (R465, R467); can land in any order.