feat(WP-67): merge behandelportal into this repo as a monorepo

Restructures into apps/ssp + apps/behandelportal (two Angular projects)
plus libs/shared + libs/beheer (cross-app libraries), replacing WP-61's
separate sibling repo. That split had already produced real drift: a
hand-vendored copy of the backend's OpenAPI doc, a shared/ui+layout tree
forked and silently diverging (7 files), and beheer + the styles.scss
token bridge duplicated byte-for-byte across both repos.

- git mv the SSP's src/app/* into apps/ssp/; fold shared/, beheer/,
  environments/, the Storybook docs/*.mdx, and styles.scss into
  libs/shared + libs/beheer (all confirmed identical between the two
  repos before merging). auth stays deliberately duplicated per
  ADR-0002 (actor-specific, expected to diverge) - amended there.
- One generated API client (libs/shared), no more vendored swagger.json.
- .dependency-cruiser split into a base factory + one config per app,
  and Storybook into .storybook-ssp/.storybook-behandelportal - both
  forced by the @auth/* alias resolving to different directories per app.
- SiteHeaderComponent/ShellComponent gained HEADER_NAV_ITEMS/
  HEADER_ADMIN_LINKS/DEBUG_PANEL injection tokens so each app supplies
  its own nav/admin-links/dev-panel instead of one being hardcoded.
- CLAUDE.md, ARCHITECTURE.md, dependencies.md, and ADR-0002 updated;
  WP-67 backlog entry documents the full decision trail.

npm run ci green (lint, dep:check x2, 360 tests across ssp/
behandelportal/shared/beheer, both localized builds, backend tests,
snippet + api-client drift); both dev servers, both Storybook
instances, and docker compose verified working.

The old sibling repo (/home/eho/repos/behandelportal) is left
untouched, not deleted.

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

libs/shared/src/application/history.ts

@@ -0,0 +1,53 @@
+import { Signal, computed, signal } from '@angular/core';
+
+export interface History<T> {
+  readonly canUndo: Signal<boolean>;
+  readonly canRedo: Signal<boolean>;
+  /** Push a pre-edit snapshot onto the undo stack and drop the redo stack. */
+  record(snapshot: T): void;
+  /** Undo: pop the last recorded snapshot and return it (moving `current` onto the redo
+      stack); returns undefined and changes nothing when there's nothing to undo. */
+  undo(current: T): T | undefined;
+  /** Redo: mirror of undo. */
+  redo(current: T): T | undefined;
+  clear(): void;
+}
+
+/**
+ * Generic undo/redo history over an immutable "document" value `T`. Elm-store editors
+ * restore a returned snapshot by re-dispatching a `Seed`-style Msg — this helper only
+ * shuffles references, it never mutates them, so the caller must hold copy-on-write state
+ * (every edit produces a fresh value). Both stacks are capped so a long session can't grow
+ * unbounded. Extracted from BriefStore's WP-27 undo/redo (WP-31); reused by the stamdata
+ * editor (WP-32).
+ */
+export function createHistory<T>(cap = 50): History<T> {
+  const past = signal<readonly T[]>([]);
+  const future = signal<readonly T[]>([]);
+  return {
+    canUndo: computed(() => past().length > 0),
+    canRedo: computed(() => future().length > 0),
+    record(snapshot) {
+      past.update((p) => [...p, snapshot].slice(-cap));
+      future.set([]);
+    },
+    undo(current) {
+      const p = past();
+      if (p.length === 0) return undefined;
+      past.set(p.slice(0, -1));
+      future.update((f) => [...f, current].slice(-cap));
+      return p[p.length - 1];
+    },
+    redo(current) {
+      const f = future();
+      if (f.length === 0) return undefined;
+      future.set(f.slice(0, -1));
+      past.update((p) => [...p, current].slice(-cap));
+      return f[f.length - 1];
+    },
+    clear() {
+      past.set([]);
+      future.set([]);
+    },
+  };
+}