Split the Enterprise Edition out into its own repository

[sinaci]

Phase 2 of the Community/Enterprise split: this repository becomes the Community Edition.

What changes

• The 13 enterprise modules (server, server-common, redcap, connector-kafka, connector-fhir-server,
  format-json, format-delta, sink-omop, runtime-streaming, runtime-scheduling, observability,
  terminology-tools, rxnorm) move to the private ignifyr/ignifyr-enterprise repository on
  gitlab.srdc.com.tr, with their history. They are deleted here by a normal commit; history is untouched.
• Community library modules are published to SRDC Nexus (not Maven Central), because the enterprise
  build's parent is this repository's root pom. ignifyr-cli is not deployed. A new deploy-snapshot
  CI job publishes main's snapshot on every push (needs the NEXUS_USERNAME/NEXUS_PASSWORD secrets;
  skips with a warning without them).
• The flatten plugin now uses resolveCiFriendliesOnly, and managed io.ignifyr versions are
  ${revision}, so the deployed root pom keeps its build configuration and pins community versions
  correctly for an inheriting child.
• The edition, release-readiness and test scripts, and all docs, are reduced to the community side.

Commits: build (Nexus publishing) · refactor (remove enterprise modules) · docs.

Verified locally (JDK 11): short tier 176 tests / 8 modules; long tier green;
check-test-tiers, check-editions (28/28), check-enforcer-gate, check-release-ready (dev mode).
The enterprise repository builds and passes its tests (241, short + long) against this branch's
snapshot, deployed to Nexus.