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>

packages/database/prisma/schema.prisma

@@ -37,9 +37,14 @@ enum ServiceKind {
   OTHER
 }
 
+/// Ordered access tier (rank): ADMIN > MANAGER > STAFF > VIEWER. VIEWER is the
+/// read-only role; STAFF and above can write. Enforced by the API's ability
+/// matrix (apps/api/src/auth/abilities.ts), not by the enum itself.
 enum UserRole {
   ADMIN
+  MANAGER
   STAFF
+  VIEWER
 }
 
 // ---------------------------------------------------------------------------