feat(auth): role-based permissions + user management (plan phase 1)

Adds the RBAC foundation the CRUD phases build on, and the first write
module (users). The platform was read-only: every controller was guarded
only by AuthenticatedGuard and UserRole was ADMIN|STAFF. The old PHP app
stored level+role but enforced neither, so this is a fresh design.

Permission model (server-authoritative):
- UserRole expanded to an ordered rank ADMIN > MANAGER > STAFF > VIEWER.
  VIEWER is the read-only role; STAFF+ can write.
- auth/abilities.ts: ROLE_RANK + ABILITY_MIN matrix + can()/abilitiesFor().
- @RequireAbility decorator + AbilityGuard enforce it on write routes;
  reads stay on AuthenticatedGuard so any logged-in user can read.
- /auth/login and /auth/me now return the resolved abilities map, so the
  web gates its UI off one payload instead of duplicating the rules.

User management (ADMIN-only, ability "user:manage"):
- UsersService gains list/create/update/resetPassword (argon2), never
  returns passwordHash; blocks self-deactivation and self-demotion;
  maps duplicate email to 409.
- UsersController: GET/POST /users, PATCH /users/:id,
  POST /users/:id/reset-password.
- Every mutation logged via new AuditService over the existing
  ActivityLog model (global CommonModule).

Web:
- AuthContext + useAuth/useCan; AppShell provides the user and gates the
  new "Usuarios" nav entry on user:manage; shows the user's role.
- /usuarios admin page: list + create/edit form + password reset +
  active toggle, Spanish-first, reusing existing card/table/field styles.

Schema pushed to dev (enum only, non-destructive). Verified end-to-end
against dev: admin CRUD works, VIEWER writes 403 while reads 200,
self-lockout guards and duplicate-email 409 all hold.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/web/src/lib/abilities.ts

@@ -0,0 +1,24 @@
+// UI-side permission helpers. The rules themselves live server-side
+// (apps/api/src/auth/abilities.ts) and arrive resolved on `user.abilities` via
+// /auth/me — this module just reads that map. Gating here is cosmetic (show or
+// hide a control); the API enforces every write regardless.
+
+import { createContext, useContext } from "react";
+import type { Ability, AuthUser } from "./types";
+
+export const AuthContext = createContext<AuthUser | null>(null);
+
+/** The signed-in user (or null while loading). */
+export function useAuth(): AuthUser | null {
+  return useContext(AuthContext);
+}
+
+/** Whether the current user may perform `ability`. False when not loaded. */
+export function useCan(ability: Ability): boolean {
+  const user = useAuth();
+  return user?.abilities?.[ability] ?? false;
+}
+
+export function can(user: AuthUser | null, ability: Ability): boolean {
+  return user?.abilities?.[ability] ?? false;
+}