feat: add Layer 2 - WhatsApp Core logic, API Gateway models/auth, Frontend core

WhatsApp Core:
- SessionManager with Baileys integration for multi-account support
- Express server with REST API and Socket.IO for real-time events
- Session lifecycle management (create, disconnect, delete)
- Message sending with support for text, image, document, audio, video

API Gateway:
- Database models: User, WhatsAppAccount, Contact, Conversation, Message
- JWT authentication with access/refresh tokens
- Auth endpoints: login, refresh, register, me
- Pydantic schemas for request/response validation

Frontend:
- React 18 app structure with routing
- Zustand auth store with persistence
- API client with automatic token handling
- Base CSS and TypeScript declarations

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

services/api-gateway/app/schemas/auth.py

@@ -0,0 +1,45 @@
+from pydantic import BaseModel, EmailStr
+from typing import Optional
+from uuid import UUID
+from app.models.user import UserRole, UserStatus
+
+
+class LoginRequest(BaseModel):
+    email: EmailStr
+    password: str
+
+
+class TokenResponse(BaseModel):
+    access_token: str
+    refresh_token: str
+    token_type: str = "bearer"
+
+
+class RefreshRequest(BaseModel):
+    refresh_token: str
+
+
+class UserResponse(BaseModel):
+    id: UUID
+    email: str
+    name: str
+    role: UserRole
+    status: UserStatus
+    is_active: bool
+
+    class Config:
+        from_attributes = True
+
+
+class LoginResponse(BaseModel):
+    access_token: str
+    refresh_token: str
+    token_type: str = "bearer"
+    user: UserResponse
+
+
+class CreateUserRequest(BaseModel):
+    email: EmailStr
+    password: str
+    name: str
+    role: UserRole = UserRole.AGENT