feat: close stub-page gaps - profile login/logout, admin Reports/Settings, Help/Docs links

Sprint A: storefront header profile control (login/logout only, no menu),
wired to existing customer Telegram auth (AuthService).

Sprint B: backoffice/reports page, reuses AdminAnalyticsFacade (Sales,
Top Products, Marketplace Health cards + CSV export).

Sprint C: backoffice/settings page, admin UI density preference
(comfortable/compact), localStorage-persisted, applied to app-table
across all admin list pages.

Sprint D: admin bottom-nav Help -> mailto using existing supportEmail,
Documentation -> external link via new TenantConfig.documentationUrl.
AdminNavLink gains externalHref for non-routerLink nav entries.

Docs: docs/GLOBAL-SPRINT-PLAN.md tracks the full sprint breakdown.
docs/COMING-SOON-AUDIT.md removed, folded into docs/KNOWN-ISSUES.md.
docs/BACKEND.md updated with the new documentationUrl bootstrap field.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/KNOWN-ISSUES.md

@@ -39,3 +39,7 @@ Condensed — full detail in commit history and `docs/RELEASE_REPORT.md`.
 - `primeng`/`primeicons` unused dependency — removed.
 - Builder static-page body editor hidden inside a mislabeled collapsed section — un-hidden, relabeled.
 - Several project-editor/admin-categories correctness bugs (footer icon id collisions, features toggle only driving one flag, languages silent duplicate no-op, static-pages slug collision, branding `socialImageUrl` never read, media-picker facade filter leakage between dialogs, categories draft-recovery/drag-reorder bugs, hardcoded locale-tab order) — see git history for the full per-bug list.
+- `HeaderConfig.showProfile` dead toggle — wired up (login/logout only, no dropdown), reuses the existing customer Telegram `AuthService`.
+- Admin `reports` nav stub — real page (`backoffice/reports`), reuses `AdminAnalyticsFacade` for Sales/Top Products/Marketplace Health cards with CSV export.
+- Admin `settings` nav stub — real page (`backoffice/settings`), UI density preference (comfortable/compact), persisted to `localStorage`, applied to admin list tables.
+- Admin `documentation`/`help` nav stubs — both wired to real external links (`mailto:` support email, `tenant.documentationUrl`).