- SyncGatewayVersion.parse() and EdgeServerVersion.parse(): prevent
  empty version string (now returns 'unknown'), catch ValueError on
  non-numeric build numbers, add warning logs for unexpected formats
- SyncGateway.get_version() and EdgeServer.get_version(): replace
  assert with graceful fallback when version string lacks '/' separator,
  use rsplit to handle multiple slashes
- GreenboardUploader.upload(): accept CouchbaseVersion object instead
  of pre-formatted string to eliminate fragile serialize-then-reparse
  pattern; use .version/.build_number directly for SGW jobs
- greenboard_fixture.py: pass CouchbaseVersion object directly instead
  of constructing intermediate string
- Add unit tests for version parsing edge cases (14 tests)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>