[DSL] 7.2 Parameter binding

**Size:** M **Description:** Implement secure parameter binding for injection prevention. **Implementation:** ```typescript // Placeholder support const query = ESQL .from('employees') .where(E('name').eq(E('?'))) // Placeholder await client.esql.query({ query, params: [userInput] // Safe binding }) // Named parameters .where(E('name').eq(E(':name'))) // params: { name: userInput } ``` **Acceptance:** - [ ] `?` positional placeholders work - [ ] `:name` named placeholders work - [ ] Params passed separately to ES - [ ] Injection attempts are safe - [ ] Unit tests for security cases