docs: writing pass — fix inconsistencies, add intros, clean boilerplate
- README.md: fix max files limit (1000 not 2000), add 300MB size limit
- deployment.md: fix port conflict (firehose HEALTH_PORT 3001→3002)
- docs/README.md: replace starlight starter boilerplate with actual content
- webhook-service README.md: replace bun init boilerplate with real docs
- index.mdx: rewrite truncated ending, add how-it-works section
- monitoring.md: add intro explaining what the integration does
- grafana-setup.md: improve intro
- bun.lock: updated from starlight build