Add Apache Spark / Amazon EMR connector decision and runtime

[intraq-dev-ai]

Connector gap

WrenAI lists Apache Spark / Amazon EMR as supported data sources. IntraQ maps Spark-like dialect behavior to Databricks in some helpers, but does not have a standalone Spark/EMR connector.

Evidence

WrenAI docs/README list Apache Spark and Amazon EMR. IntraQ live SQL execution currently supports Databricks SQL, but not a generic Spark Thrift Server or EMR connector.

Acceptance criteria

• Decide whether Spark/EMR is supported as a standalone connector or explicitly documented as unsupported.
• If supported, add connection fields for Spark Thrift Server / EMR endpoint configuration.
• Support discovery, query preview, SQL Editor execution, Analyzer, and Dashboard Builder.
• Add tests for connection validation, limits, and Spark SQL dialect behavior.