Add CRD field validation annotations

Support Kubernetes validation annotations in CRD types.

**Example:**
```rust
#[schemars(range(min = 1, max = 100))]
replicas: i32,

#[schemars(regex = "^[a-z]+$")]
name: String,
```

**Acceptance Criteria:**
- Common validation patterns
- Integration with schemars
- Generated OpenAPI validation