Publish querydsl-bom as a real module so it auto-deploys to Central

[velo]

Problem

querydsl-bom was missing from Maven Central for 7.2 (see #1444), while every other 7.2 artifact was present. Root cause: the BOM is produced by sundr-maven-plugin:generate-bom, but sundr's template emits no <build>, so its self-deploy never goes through the central-publishing-maven-plugin portal publisher. Every prior BOM (7.1, …) had to be uploaded manually. The generated BOM also wrongly included querydsl-apt-test, which is excluded from Central deploy.

(7.2 BOM has been published manually to unblock users; this PR fixes the build so it never happens again.)

Fix

Keep sundr as the generator (preserving module auto-discovery), but make the BOM a real committed module that publishes through the same path as every other artifact:

• src/main/resources/bom-template.xml.vm — custom sundr template emitting a parent-based module pom (inherits the release profile: gpg + central-publishing) instead of a standalone pom.
• querydsl-bom/pom.xml — the generated BOM, committed and wired into <modules>; it now deploys like querydsl-core.
• sundr <goals> exclude install/deploy — sundr only writes the file; it no longer attempts its broken self-deploy.
• excludes *:querydsl-bom (no self-reference) and *:querydsl-apt-test (not deployed to Central).

Regenerating when modules change

mvn -Pquickbuild validate
cp target/classes/querydsl-bom/pom.xml querydsl-bom/pom.xml
git add querydsl-bom/pom.xml && git commit

Verified

• querydsl-bom validates and builds in the reactor.
• Under -Prelease the module is gpg-signed and central-publishing engages (same path as querydsl-core).
• sortpom is idempotent on the generated pom, so the regenerate→commit workflow is stable.