feat(i18n): complete admin app internationalization across all pages

fix(audit): resolve remaining minor technical debt issues

feat: complete agentic audit roadmap — retry, KB generate, real costs, traceId, rate-limit

fix(conversations): resolve /conversations blank page + slug→UUID KB routes + WABA banner

refactor(debt): resolve all 10 technical debt items from audit

feat: wire i18n to all remaining admin pages

chore: stabilization, audit fixes and project synchronization