Use dataclasses or Pydantic for data structures

Use dataclasses for simple data containers, Pydantic for validation:

```python
from dataclasses import dataclass
from pydantic import BaseModel

# Simple data container
@dataclass
class Point:
x: float
y: float

# With validation (API models, config)
class UserCreate(BaseModel):
email: str
name: str
age: int = Field(ge=0, le=150)
```

Avoid plain dicts for structured data - they lack type safety and validation.