docs: archive the finished backlogs (RD-30)

Two backlog trees are complete: `docs/project/backlog/` (75 files, every
WP done) and `docs/project/refactor-backlog-setup/` (the arc before it).
Move both under `docs/project/archive/` with `git mv`, so history stays
intact through `git log --follow`. `SHOWCASE-ROADMAP.md` moves with them,
because it points at the now-archived backlog README.

Add `docs/project/archive/README.md`. It states that these trees are
historical and names the two directories that are still live.

Repoint every inbound reference named in RD-30's Files table: CLAUDE.md,
the root README, both backend READMEs, `LetterHtml.cs`, `a11y.mdx`, the
`document-feature` and `new-ssp` skills, and the readable-codebase PLAN,
README, and RD-19 ticket. Fix two upward-relative links inside the moved
WP files (WP-68, WP-69) that gained a directory level and would otherwise
break. Repoint `.prettierignore`'s two agent-prompt exclusions to their
new path, so prettier keeps leaving those files' exact wording alone.

Mark RD-30 done and check off its acceptance criteria; flip its README
row to done.

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

docs/project/archive/backlog/WP-45-create-frontend-generator.md

@@ -0,0 +1,32 @@
+# WP-45 — `create-frontend` bootstrap generator
+
+Status: done (ad7ca31)
+Phase: 8 — platform/DX/showcase
+Priority: P4
+Depends on: WP-43, WP-44
+
+## Why
+
+`new-ssp` is a manual fork-and-strip recipe. To actually bootstrap a production-ready frontend for
+a different Dutch register quickly, mechanise it into a runnable script that produces a clean
+scaffold keeping the enforced architecture + shared building blocks.
+
+## Decisions
+
+- A `create-frontend` script (Node/plop-driven) that clones-and-strips per the `new-ssp` recipe:
+  drop the business contexts, prune their routes/aliases/boundary entries, rename `BigRegister.*`,
+  re-point the `--rhc-*` token bridge, re-seed the backend, re-run `gen:api`.
+- Keep-as-is list from `new-ssp` (shared kernel/ui/layout, eslint/boundary config, check-tokens,
+  CI, nswag, storybook, auth shell, ADRs, CLAUDE.md, the skills).
+- Reuse WP-44's `gen:context` to seed the first real context of the new portal.
+
+## Files
+
+- New `scripts/create-frontend.*` (+ any templates); documented in `.claude/skills/new-ssp/SKILL.md`.
+
+## Acceptance criteria
+
+- [ ] Running it yields a portal that builds, lints (boundaries intact), and passes `npm run ci`
+      with no business contexts left over.
+- [ ] The generated scaffold's `gen:api` + token bridge point at the new backend/theme.
+- [ ] Documented end-to-end in the `new-ssp` skill.