chore: archive legacy Identity, Workday, and Intune folders

- Move Identity/, Workday/, Intune/ to archive/ (superseded by nexus-mcp shards)
- Move 'Local Setup.md' to archive/ (superseded by nexus-mcp/Local-Setup.md)
- Add archive/README.md explaining migration and preserved content
- Clean repository structure: only nexus-mcp, documentation, and .github remain active

All legacy functionality migrated to nexus-mcp sharded architecture.
Archived folders preserved for reference and historical context.

Refs: SESSION_SNAPSHOT_2026-04-13.md

archive/Identity/.gitignore

@@ -0,0 +1,7 @@
+__pycache__/
+*.pyc
+.venv/
+.pytest_cache/
+*.pyc
+.coverage
+htmlcov/