Fix workflow cleanup to remove executions-backed run summaries

[santoshkumarradha]

Summary

• extend workflow cleanup target resolution to include run IDs from executions and workflow_executions
• delete execution-backed run summary data during cleanup (executions, execution_webhooks, execution_webhook_events)
• delete workflow_runs as part of cleanup to keep legacy metadata consistent
• include these tables in cleanup result counters for visibility
• add regression tests, including a non-FTS in-memory test that validates execution-table cleanup

Root cause

/api/ui/v2/workflow-runs is built from executions (QueryRunSummaries).
Cleanup previously deleted workflow-scoped tables but left executions rows intact, so runs still appeared in the UI even after DELETE .../cleanup returned 200.

Validation

• go test ./internal/storage -run "TestLocalStorageCleanupWorkflowDeletesExecutionRecordsWithoutFTS|TestLocalStorageCleanupWorkflowByRunID" -v
• go test ./internal/storage
• go test ./internal/server -run TestSetupRoutesRegistersWorkflowCleanupUIRoute

Issue

Closes #175

[santoshkumarradha]

Superseded by #177 (clean branch from origin/main with only the new cleanup fix).