docs: move the LOTUS_TODO / LOTUS_TESTING backlogs into Gitea issues; keep a reference-only LOTUS_REFERENCE.md

LOTUS_TODO.md → LOTUS_REFERENCE.md (design laws, decided deferrals,
server-blocked features, operational reference only). Every open task was
filed: cinny #195–#210, cinny-desktop #15–#18, matrix #8–#10.

LOTUS_TESTING.md keeps the automated-coverage map, the Playwright notes and
the deploy tip; every manual checklist is now a `qa` issue under the
'Manual QA backlog' (cinny #170–#194, #198) and 'Desktop QA backlog'
(cinny-desktop #11–#14, #18) milestones.

Repointed the README, LOTUS_FEATURES, CI and source comments that
referenced LOTUS_TODO.md.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

.gitea/workflows/ci.yml

@@ -239,7 +239,7 @@ jobs:
   #                 below are set (create them under repo → Settings → Actions
   #                 → Secrets; they are empty until then).
   # dist/ is rebuilt in-job because actions/upload-artifact@v4 does not work
-  # on this Gitea runner (LOTUS_TODO), so `needs: build` only gates on the
+  # on this Gitea runner (see LOTUS_REFERENCE.md → CI/CD), so `needs: build` only gates on the
   # main job having passed, not on its artifact.
   # Hard gate: proven green on the runner in run #1880 (chromium + deps
   # install fine there). The E2EE tier self-skips without the E2E_* secrets.