feat(agent): event timeline API, SSE stream, Coolify DDL, env template

- Add agent_session_events table + GET/POST events + SSE stream routes
- Build Agent tab: hydrate from events + EventSource while running
- entrypoint: create agent_sessions + agent_session_events on container start
- .env.example for AGENT_RUNNER_URL, AGENT_RUNNER_SECRET, DATABASE_URL

Made-with: Cursor

.gitignore

@@ -32,6 +32,7 @@ yarn-error.log*
 
 # env files (can opt-in for committing if needed)
 .env*
+!.env.example
 
 # vercel
 .vercel