docs(07): create phase plan — 5 plans, verification passed
5 waves: system_settings DB + HKDF encryption (01), ProviderConfig +
GenericOpenAIProvider + singleton client fix (02), Anthropic output_config +
classifier wiring (03), Celery retry 30/90/270s + re-queue endpoint (04),
admin AI panel + DocumentCard badge + human checkpoint (05).
All 18 decisions D-01..D-18 covered. Plan checker passed after 1 revision
round (4 blockers fixed: D-02/D-14 coverage, D-11 Vitest tests, Plan 05
files_modified).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
