Migrate healthcare-assistant demo app from galileo to splunk-ao SDK

[etserend]

Summary

• Migrates all three healthcare-assistant workshop variations (2-app-with-instrumentation, 3-app-with-experiments, 4-app-with-controls) from the galileo SDK to splunk-ao
• Updates credentials (GALILEO_* → SPLUNK_AO_*), callbacks (GalileoAsyncCallback → SplunkAOAsyncCallback), logger (GalileoLogger → SplunkAOLogger), context manager (galileo_context → splunk_ao_context), and k8s configmap references (galileo-config → splunk-ao-config)
• Updates Agent Control SDK deps (agent-control-sdk[galileo] → agent-control-sdk[splunk-ao]) and API key header (Galileo-API-Key → Splunk-AO-Key) in 4-app
• Updates all corresponding workshop content pages (en + ja) with new package names, credential names, image references, and console UI steps

Test plan

• Verify 2-app-with-instrumentation starts and traces appear in Splunk AO console under configured project/agent stream
• Verify 3-app-with-experiments dataset creation and experiment run complete successfully with SplunkAOEvaluators metrics
• Verify 4-app-with-controls Agent Control initializes on startup, blocking control stops DELETE SQL, steering control redacts PII from LLM response
• Confirm workshop content pages render correctly (no broken image refs, correct code snippets)

Closes HYBIM-977