feat: complete agent monitoring - hook, UI, and backend filter

- Add event_type and framework filters to events query endpoint
- Add /agents SPA route to web-ui server
- Add Agents nav link and route in frontend
- Add agents page CSS (timeline, VM pills, stats panel)
- Build VM status strip, activity timeline, and real-time stats
- Add agentmon hook for OpenClaw (HOOK.md + handler.ts)
- Add docker-compose, Dockerfile, and supporting infra files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,14 @@
+# Local development configuration
+# Copy this file to .env and adjust as needed
+
+# Postgres database (running via docker-compose)
+DATABASE_URL=postgres://postgres:pass@localhost:5432/agentmon?sslmode=disable
+
+# NATS message queue (running via docker-compose)
+NATS_URL=nats://localhost:4222
+
+# NATS topic for events
+NATS_TOPIC=agentmon.events.v1
+
+# Query API base URL (for web-ui proxy)
+AGENTMON_QUERY_BASE=http://localhost:8081