Vendor hibernia-framework source as a submodule pinned at v1.1.0

Add https://github.com/ParadauxIO/hibernia-framework as a git submodule at hibernia-framework/, pinned to commit 84157ce (tag v1.1.0, matching the dependency bump in PAR-246), so the framework source is available in-workspace for reference.

Build impact: none. settings.gradle.kts uses explicit include(...) and does not include the submodule, so it is not compiled as a Gradle project (./gradlew projects unchanged); the build still consumes io.paradaux:hibernia-framework:1.1.0 as a published artifact. CI checkout doesn't init submodules, so CI is unaffected. This realises the submodule layout already described in CLAUDE.md / the wiki.