feat(saas): update schema for db-per-tenant and per-component FIEL encryption

- Rename Tenant.schemaName to databaseName across all services
- Add Subscription and Payment models to Prisma schema
- Update FielCredential to per-component IV/tag encryption columns
- Switch FIEL encryption key from JWT_SECRET to FIEL_ENCRYPTION_KEY
- Add Subscription and Payment shared types
- Update JWTPayload to use databaseName

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/middlewares/tenant.middleware.ts

@@ -29,17 +29,17 @@ export async function tenantMiddleware(req: Request, res: Response, next: NextFu
 
     const tenant = await prisma.tenant.findUnique({
       where: { id: tenantId },
-      select: { schemaName: true, active: true },
+      select: { databaseName: true, active: true },
     });
 
     if (!tenant || !tenant.active) {
       return next(new AppError(403, 'Tenant no encontrado o inactivo'));
     }
 
-    req.tenantSchema = tenant.schemaName;
+    req.tenantSchema = tenant.databaseName;
 
-    // Set search_path for this request
-    await prisma.$executeRawUnsafe(`SET search_path TO "${tenant.schemaName}", public`);
+    // Set search_path for this request (will be replaced by pool-based approach)
+    await prisma.$executeRawUnsafe(`SET search_path TO "${tenant.databaseName}", public`);
 
     next();
   } catch (error) {