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/api/src/auth/ability.guard.ts

@@ -0,0 +1,36 @@
+import {
+  CanActivate,
+  ExecutionContext,
+  ForbiddenException,
+  Injectable,
+} from "@nestjs/common";
+import { Reflector } from "@nestjs/core";
+import { Request } from "express";
+import { ABILITY_KEY } from "./require-ability.decorator";
+import { Ability, Role, can } from "./abilities";
+
+/**
+ * Enforces the ability matrix (abilities.ts) against req.user.role. A route
+ * with no @RequireAbility passes through untouched — this guard only gates the
+ * routes that declare one. It does NOT check authentication; always list it
+ * after AuthenticatedGuard so an unauthenticated request is rejected first.
+ */
+@Injectable()
+export class AbilityGuard implements CanActivate {
+  constructor(private readonly reflector: Reflector) {}
+
+  canActivate(context: ExecutionContext): boolean {
+    const ability = this.reflector.getAllAndOverride<Ability | undefined>(
+      ABILITY_KEY,
+      [context.getHandler(), context.getClass()],
+    );
+    if (!ability) return true;
+
+    const req = context.switchToHttp().getRequest<Request>();
+    const user = req.user as { role?: Role } | undefined;
+    if (!user?.role || !can(user.role, ability)) {
+      throw new ForbiddenException("No tiene permisos para esta acción");
+    }
+    return true;
+  }
+}