feat(auth): authorization catalogues + Principal builder skeleton (ADR-0025)

Per ADR-0025's implementation phasing, lands the closed-set
catalogues + the OIDC-callback hook that composes the
session-resident Principal. No new guards yet.

- libs/shared/auth: framework-agnostic lib hosting
  authorization.types.ts (4 privileges + 24 functional roles + 6
  scope kinds + Principal type) and entra-group-to-role.ts
  (validated GUID -> slug resolver). 17 unit tests against the
  catalogues + resolver contracts.
- BFF: PrincipalBuilder composes the three axes once at sign-in;
  ScopeResolver seam (StubScopeResolver returns unrestricted in
  v1, replaced by a Prisma-backed implementation when ADR-0026's
  user_scopes table lands). 19 persona-driven tests covering the
  test tenant's full provisioning + edge cases (unknown
  privilege drift, unknown group GUID, empty permissions).
- AuthService extracts the Entra "groups" claim; AuthenticatedUser
  grows the groups: readonly string[] field.
- SessionEstablisher builds + persists the principal alongside
  the legacy user shape (additive — guards consuming user.oid
  unchanged).
- ENTRA_GROUP_MAP_PATH env var + load-entra-group-map.ts read
  the tenant-private map from infra/<env>-tenant.entra.json
  (gitignored; .example.json committed with the schema).
- ADR-0025 path references updated from libs/feature/auth
  (Angular-scoped, scope:portal-shell) to libs/shared/auth
  (consumable by both BFF and SPA).
- notes/entra-groups-claim-activation.md: operator runbook for
  the "Token configuration -> Add groups claim" step in the
  Entra admin centre.

Test plan:
- pnpm nx affected -t lint test build : 13 projects green
  (497 BFF tests + 17 shared-auth tests + 1 shared-util test +
  full lint + full build).

apps/portal-bff/src/auth/entra-group-to-role.token.ts

@@ -0,0 +1,12 @@
+/**
+ * DI token for the lazily-loaded `EntraGroupToRoleResolver`.
+ *
+ * The resolver wraps a `Map<groupGuid, FunctionalRole>` parsed
+ * once at boot from `infra/<env>-tenant.entra.json` (per ADR-0025
+ * §"Sources of truth — Entra-side configuration"). The token is
+ * separate from the class import so the BFF can swap the
+ * implementation (an empty-map stub when no file is configured,
+ * a real one when `ENTRA_GROUP_MAP_PATH` resolves) without the
+ * consumers caring.
+ */
+export const ENTRA_GROUP_TO_ROLE_RESOLVER = Symbol('ENTRA_GROUP_TO_ROLE_RESOLVER');