feat(fp): WP-23 — org-template backend + admin role

Second template axis (org identity: letterhead, footer, signature,
margins) server-side: OrgTemplateStore with JSON version history,
publish/rollback, sent-brief version pinning, admin role + capability,
5 admin endpoints, org-logo upload category. FE seam widened only
(Role/Capability unions, interceptor); WP-24/26 consume it.

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

docs/backlog/WP-26-org-template-editor.md

@@ -0,0 +1,90 @@
+# WP-26 — Admin org-template editor
+
+Status: todo
+Phase: 6 — Brief v2 (edit-on-the-letter, org templates, server-rendered preview)
+
+## Why
+
+The org template (WP-23) needs its editor: an admin edits, per sub-organization, the
+letter's appearance **in place on the same canvas** the drafter composes on — the
+mirror image (`editableRegions='template'`: letterhead/footer/signature editable,
+content a read-only sample). PRD Brief v2 §5, §7h.
+
+## Read first
+
+- PRD Brief v2 §5, §7h; `docs/backlog/WP-23/24/25` (endpoints, canvas, proefbrief)
+- `src/app/shared/application/access.store.ts` (`can('orgtemplate:edit')`)
+- `.claude/skills/form-machine` — the house form idiom this editor follows
+- `src/app/shared/ui/upload/single-upload` (logo upload reuse)
+
+## Decisions (pre-made, don't relitigate)
+
+- **Lives in the `brief` context** (route `/brief/huisstijl`, lazy) — same bounded
+  capability, no new context. Gated by `AccessStore.can('orgtemplate:edit')` with a
+  denial alert (deny-by-default); no new route guard.
+- **House form-machine idiom**: `org-template.machine.ts`
+  (`OrgTemplateState`/`OrgTemplateMsg`, pure `reduce` + spec) — draft fields are form
+  state, not brief state. Store (`org-template.store.ts`, root singleton) does
+  debounced draft save (mirror `BriefStore.scheduleSave`), publish, rollback.
+- **Publish shows impact first**: confirmation displays the WP-23 impact count
+  ("Dit raakt N nog niet verzonden brieven") before the POST.
+- **Version history is a list, rollback copies into draft** (WP-23 semantics) —
+  no side-by-side rendered diff (deferred; field-level history list is enough here).
+- **Logo upload reuses `single-upload`** against the `org-logo` category; the canvas
+  shows `<img src="/api/v1/uploads/{id}/content">`.
+- **Proefbrief** = the WP-25 admin preview endpoint; just a button.
+- Margins are bounded number inputs (server re-validates, WP-23).
+
+## Files
+
+- `src/app/brief/domain/org-template.machine.ts` (+spec)
+- `src/app/brief/application/org-template.store.ts`
+- `src/app/brief/infrastructure/org-template.adapter.ts` (+spec, `parseOrgTemplateAdminView`)
+- `src/app/brief/ui/org-template-editor/*` (organism + stories)
+- `src/app/brief/ui/org-template.page.ts`
+- `src/app/app.routes.ts` (route `brief/huisstijl`)
+
+## Steps
+
+1. Machine (fields, `FieldEdited`/`MarginEdited`/`LogoSet`/`DraftLoaded`/save-publish
+   outcome Msgs) + spec.
+2. Adapter (generated client CRUD + parse boundary) + spec.
+3. Store: load (sub-org list + selected), debounced save, publish (impact confirm),
+   rollback.
+4. Editor UI: sub-org switcher, canvas in `'template'` mode with inline-editable
+   regions, margins inputs, logo upload, version history + rollback, proefbrief
+   button, publish bar showing live version + published-at.
+5. Route + capability gate + stories (axe).
+
+## Acceptance criteria
+
+- [ ] `?role=admin` can switch sub-orgs, edit all template fields in place on the
+      canvas, and see the canvas update live.
+- [ ] Draft saves are debounced; publish asks for confirmation showing the impact
+      count; after publish the drafter's canvas (WP-24) reflects it on reload.
+- [ ] Version history lists published versions (who is faked, when is real);
+      rollback copies an old version into the draft.
+- [ ] Non-admin on `/brief/huisstijl` sees the denial alert; API would 403 anyway.
+- [ ] Logo upload validates type/size client-side (existing `rejectReason`) and
+      renders on the canvas after upload.
+- [ ] Machine spec covers field edits, dirty tracking, publish/rollback outcomes.
+- [ ] Full GREEN.
+
+## Verification
+
+GREEN one-liner; manual walk: admin edits footer + margin → canvas live-updates →
+proefbrief shows draft → publish (impact count) → `?role=drafter` reload shows new
+appearance; second sub-org unaffected.
+
+## Out of scope
+
+Template approval chain (four-eyes on templates — PRD open question, out for POC).
+Rendered side-by-side version diff. Soft locks. New shared overlay/modal component —
+the publish confirmation uses the existing inline confirmation pattern, not a dialog.
+
+## Risks
+
+The editor is the first consumer of `editableRegions='template'` — WP-24 built the
+input but nothing exercised it; budget for canvas fixes here. Debounced draft save +
+publish can race — flush the draft save before publishing (same
+`clearTimeout`+`flushSave` discipline as `BriefStore.transition`).