Add Apache Superset for xAPI/LRsql analytics

[sei-awelle]

Summary

• Adds Apache Superset container to the Aspire AppHost for xAPI learning analytics
• Configures Keycloak OAuth SSO and auto-registers the LRsql database on startup
• Creates a starter "xAPI Learning Analytics" dashboard with 7 charts: client app breakdown (Blueprint, CITE, Gallery, Steamfitter), verb distribution, activity timeline, top learners, and most active learning objects

Details

• Custom Dockerfile adds psycopg2-binary and authlib to the stock Superset image
• Keycloak OAuth uses split internal/external URLs for container-to-container vs browser redirects
• Dashboard is created via Superset's internal ORM on first startup to properly populate chart associations
• Superset client added to Keycloak realm JSON
• Launch configurations and env file added for toggling Superset on/off

New files

File	Purpose
Dockerfile.SupersetCustom	Custom image with PostgreSQL + OAuth deps
superset_config.py	OAuth, cache, security config
init-superset.sh	Startup: migrations, admin user, LRsql registration, dashboard
create-dashboard-orm.py	ORM-based dashboard creation (runs on startup)
create-dashboard.{py,js,sh}	Alternative REST API scripts for manual use
README.md	Integration documentation

Test plan

• Run aspire run with Launch__Superset=true
• Verify Superset starts and is healthy at http://localhost:8088
• Verify LRsql database appears in Superset data sources
• Verify xAPI Learning Analytics dashboard loads with charts
• Verify Keycloak OAuth login works from Superset login page
• Verify toggling Superset off excludes it from startup