refactor(B1): migrate to domain-driven project structure

Move all models/schemas/services/routers into app/domains/.
Keep backward-compat shims in old locations for imports.
Preserves domains/rendering/tasks.py from Phase A.

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

backend/app/domains/auth/schemas.py

@@ -0,0 +1,39 @@
+import uuid
+from datetime import datetime
+from pydantic import BaseModel, EmailStr
+from app.domains.auth.models import UserRole
+
+
+class UserCreate(BaseModel):
+    email: EmailStr
+    password: str
+    full_name: str
+    role: UserRole = UserRole.client
+
+
+class UserUpdate(BaseModel):
+    full_name: str | None = None
+    is_active: bool | None = None
+    role: UserRole | None = None
+
+
+class UserOut(BaseModel):
+    id: uuid.UUID
+    email: str
+    full_name: str
+    role: UserRole
+    is_active: bool
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class TokenResponse(BaseModel):
+    access_token: str
+    token_type: str = "bearer"
+    user: UserOut
+
+
+class LoginRequest(BaseModel):
+    email: EmailStr
+    password: str