docs: remove code-review.md, carry the open items into roadmap

The review's plan is finished — phase 0 (bar the two release-commit steps),
1, 1.5, 2 and 3 are all closed — and what remained in the document was a second
copy of things that already live in architecture.md, security.md, roadmap.md or
the code comments: the GUI compromise table is in panel.css/panel.js/
middleware.go/handlers_auth.go, the single SQLite connection and the dual
cookie names are explained where they are implemented, the accepted gaps are in
security.md, and the model-routing table names progress.md and development.md
as its own source. A second copy of a fact is a place for it to go stale.

Four items were genuinely open and had no other home, so they moved to
roadmap.md rather than disappearing:

- splitting internal/web into subpackages (2.x) — with the reason to wait: the
  flat package still reads at 47 files, and both 2.x features grow it, so the
  cut is worth making before that growth, not now;
- a consolidated documentation index in the README (v1.x tail);
- the adaptive polling interval for a tab that is visible but idle — the hidden
  case is already handled, and the remainder is explicitly allowed to end as
  "decided not to";
- CONTRIBUTING.md, already moved to 2.x in the previous commit.

References retargeted: progress.md (7), roadmap.md (5), implementation-plan.md
(1). The CHANGELOG entries that cite the document are left as written — they
describe what happened at the time. The review text stays in git history at
522425a.

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

docs/implementation-plan.md

@@ -4,9 +4,8 @@
 безопасности (§ D) выполнена 2026-08-06, релизный гейт (e2e + ревизия) открыт.
 B.1–B.3 и C.4 закрыты — as-built в [architecture.md](architecture.md),
 e2e/CI в [development.md](development.md), принятые риски в
-[security.md](security.md). Комплексное рецензирование кодовой базы и план
-доработок — [code-review.md](code-review.md). Текущее состояние и следующий
-шаг: [progress.md](progress.md). Объём 2.x.x — [roadmap.md](roadmap.md).
+[security.md](security.md). Текущее состояние и следующий шаг:
+[progress.md](progress.md). Объём 2.x.x — [roadmap.md](roadmap.md).
 
 **Основа:** [product.md](product.md) v1.0.