feat: add Layer 3 - API Gateway main app, WhatsApp routes, Frontend pages

API Gateway:
- main.py with FastAPI app, CORS, health endpoints
- WhatsApp routes: accounts CRUD, conversations, messages, internal events
- WhatsApp schemas for request/response validation

Frontend:
- Login page with register option for first admin
- MainLayout with sidebar navigation and user dropdown
- Dashboard with statistics cards (accounts, conversations)
- WhatsApp Accounts page with QR modal for connection
- Inbox page with conversation list and real-time chat

Full feature set for Fase 1 Foundation complete.

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

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

@@ -0,0 +1,76 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from uuid import UUID
+from datetime import datetime
+from app.models.whatsapp import AccountStatus, ConversationStatus, MessageType, MessageDirection, MessageStatus
+
+
+class WhatsAppAccountCreate(BaseModel):
+    name: str
+
+
+class WhatsAppAccountResponse(BaseModel):
+    id: UUID
+    phone_number: Optional[str]
+    name: str
+    status: AccountStatus
+    qr_code: Optional[str]
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class ContactResponse(BaseModel):
+    id: UUID
+    phone_number: str
+    name: Optional[str]
+    email: Optional[str]
+    company: Optional[str]
+    tags: List[str]
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class MessageResponse(BaseModel):
+    id: UUID
+    direction: MessageDirection
+    type: MessageType
+    content: Optional[str]
+    media_url: Optional[str]
+    status: MessageStatus
+    is_internal_note: bool
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class ConversationResponse(BaseModel):
+    id: UUID
+    contact: ContactResponse
+    status: ConversationStatus
+    last_message_at: Optional[datetime]
+    created_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class ConversationDetailResponse(ConversationResponse):
+    messages: List[MessageResponse]
+    whatsapp_account: WhatsAppAccountResponse
+
+
+class SendMessageRequest(BaseModel):
+    type: MessageType = MessageType.TEXT
+    content: str
+    media_url: Optional[str] = None
+
+
+class InternalEventRequest(BaseModel):
+    type: str
+    accountId: str
+    data: dict