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/routers/__init__.py

@@ -0,0 +1,3 @@
+from app.routers.auth import router as auth_router
+
+__all__ = ["auth_router"]

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

@@ -0,0 +1,96 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from app.core.database import get_db
+from app.core.security import (
+    verify_password,
+    get_password_hash,
+    create_access_token,
+    create_refresh_token,
+    decode_token,
+    get_current_user,
+)
+from app.models.user import User, UserRole
+from app.schemas.auth import (
+    LoginRequest,
+    LoginResponse,
+    RefreshRequest,
+    TokenResponse,
+    UserResponse,
+    CreateUserRequest,
+)
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+@router.post("/login", response_model=LoginResponse)
+def login(request: LoginRequest, db: Session = Depends(get_db)):
+    user = db.query(User).filter(User.email == request.email).first()
+
+    if not user or not verify_password(request.password, user.password_hash):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid email or password",
+        )
+
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="User account is disabled",
+        )
+
+    access_token = create_access_token(data={"sub": str(user.id)})
+    refresh_token = create_refresh_token(data={"sub": str(user.id)})
+
+    return LoginResponse(
+        access_token=access_token,
+        refresh_token=refresh_token,
+        user=UserResponse.model_validate(user),
+    )
+
+
+@router.post("/refresh", response_model=TokenResponse)
+def refresh_token(request: RefreshRequest, db: Session = Depends(get_db)):
+    payload = decode_token(request.refresh_token)
+
+    if payload.get("type") != "refresh":
+        raise HTTPException(status_code=401, detail="Invalid token type")
+
+    user_id = payload.get("sub")
+    user = db.query(User).filter(User.id == user_id).first()
+
+    if not user or not user.is_active:
+        raise HTTPException(status_code=401, detail="User not found")
+
+    access_token = create_access_token(data={"sub": str(user.id)})
+    new_refresh_token = create_refresh_token(data={"sub": str(user.id)})
+
+    return TokenResponse(access_token=access_token, refresh_token=new_refresh_token)
+
+
+@router.get("/me", response_model=UserResponse)
+def get_me(current_user: User = Depends(get_current_user)):
+    return UserResponse.model_validate(current_user)
+
+
+@router.post("/register", response_model=UserResponse)
+def register_first_admin(request: CreateUserRequest, db: Session = Depends(get_db)):
+    # Only allow if no users exist (first admin)
+    user_count = db.query(User).count()
+    if user_count > 0:
+        raise HTTPException(status_code=403, detail="Registration disabled")
+
+    existing = db.query(User).filter(User.email == request.email).first()
+    if existing:
+        raise HTTPException(status_code=400, detail="Email already registered")
+
+    user = User(
+        email=request.email,
+        password_hash=get_password_hash(request.password),
+        name=request.name,
+        role=UserRole.ADMIN,
+    )
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+
+    return UserResponse.model_validate(user)