handlers/integration.go: extract helper functions to reduce function length #72

Problem

After the connector factory refactor, ConfigureWorkflow() is still ~179 lines and ExecuteIntegrationWorkflow() is still ~133 lines. Both are too long and mix concerns.

Fix Direction

• Extract parseConnectorConfigs() from ConfigureWorkflow()
• Extract parseStepConfigs() from ConfigureWorkflow()
• Extract executeStepWithRetry() from ExecuteIntegrationWorkflow()

Each extracted function should have a single clear responsibility and be independently testable.

Context

See docs/DEFERRED_ISSUES.md — Code Smells section.