feat: add multi-tenant client management for admins

- Add tenants API endpoints (list, get, create)
- Add tenant middleware override via X-View-Tenant header
- Add TenantSelector dropdown component in header
- Add tenant view store with persistence
- Add Clientes management page
- Update all navigation layouts with Clientes link for admins

Admins can now:
- View list of all clients
- Create new clients with automatic schema setup
- Switch between viewing different clients' data
- See which client they are currently viewing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/app.ts

@@ -12,6 +12,7 @@ import { alertasRoutes } from './routes/alertas.routes.js';
 import { calendarioRoutes } from './routes/calendario.routes.js';
 import { reportesRoutes } from './routes/reportes.routes.js';
 import { usuariosRoutes } from './routes/usuarios.routes.js';
+import { tenantsRoutes } from './routes/tenants.routes.js';
 
 const app = express();
 
@@ -41,6 +42,7 @@ app.use('/api/alertas', alertasRoutes);
 app.use('/api/calendario', calendarioRoutes);
 app.use('/api/reportes', reportesRoutes);
 app.use('/api/usuarios', usuariosRoutes);
+app.use('/api/tenants', tenantsRoutes);
 
 // Error handling
 app.use(errorMiddleware);