Contacts: read character/corp/alliance contacts; guarded add/remove of
character contacts. Fittings: read saved fits; guarded create/delete.
EsiClient.delete now takes params. All writes go through write-safety.
Closes#25, #26. 120 tests, coverage 89%.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
