feat: Add batch support to Statement implementation

[michael-simons]

Summary

• Implement addBatch(String), clearBatch(), and executeBatch() on StatementImpl, replacing the previous SQLFeatureNotSupportedException stubs
• Each batch entry is executed via executeUpdate0 with SQL processing enabled, supporting both Cypher and SQL statements
• Failures throw BatchUpdateException with partial results per the JDBC specification
• Guard individual statement execution (executeQuery, executeUpdate, execute) when a batch is pending, requiring the batch to be executed or cleared first

Test plan

• shouldExecuteBatchWithCypher — multiple Cypher CREATE statements, verify node counts
• shouldExecuteBatchWithSQL — SQL INSERT statements with translation enabled
• shouldClearBatch — verify clearBatch() resets, executeBatch() returns empty array
• shouldThrowOnAddBatchWhenClosed — closed statement throws SQLException
• shouldThrowOnAddBatchWithNullSQL — null SQL throws SQLException
• shouldExecuteEmptyBatch — empty batch returns empty int[]
• shouldRejectExecuteQueryWhenBatchPending — executeQuery blocked by pending batch
• shouldRejectExecuteUpdateWhenBatchPending — executeUpdate blocked by pending batch
• shouldRejectExecuteWhenBatchPending — execute blocked by pending batch
• shouldAllowExecuteAfterClearBatch — normal execution works after clearing
• shouldAllowExecuteAfterExecuteBatch — normal execution works after batch execution

🤖 Generated with Claude Code