feat: add Prisma schema with multi-tenant support

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

apps/api/prisma/schema.prisma

@@ -0,0 +1,64 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "postgresql"
+  url      = env("DATABASE_URL")
+}
+
+model Tenant {
+  id          String    @id @default(uuid())
+  nombre      String
+  rfc         String    @unique
+  plan        Plan      @default(starter)
+  schemaName  String    @unique @map("schema_name")
+  cfdiLimit   Int       @map("cfdi_limit")
+  usersLimit  Int       @map("users_limit")
+  active      Boolean   @default(true)
+  createdAt   DateTime  @default(now()) @map("created_at")
+  expiresAt   DateTime? @map("expires_at")
+
+  users User[]
+
+  @@map("tenants")
+}
+
+model User {
+  id           String    @id @default(uuid())
+  tenantId     String    @map("tenant_id")
+  email        String    @unique
+  passwordHash String    @map("password_hash")
+  nombre       String
+  role         Role      @default(visor)
+  active       Boolean   @default(true)
+  lastLogin    DateTime? @map("last_login")
+  createdAt    DateTime  @default(now()) @map("created_at")
+
+  tenant Tenant @relation(fields: [tenantId], references: [id])
+
+  @@map("users")
+}
+
+model RefreshToken {
+  id        String   @id @default(uuid())
+  userId    String   @map("user_id")
+  token     String   @unique
+  expiresAt DateTime @map("expires_at")
+  createdAt DateTime @default(now()) @map("created_at")
+
+  @@map("refresh_tokens")
+}
+
+enum Plan {
+  starter
+  business
+  professional
+  enterprise
+}
+
+enum Role {
+  admin
+  contador
+  visor
+}