ci(observer): verify clean Compose quickstart

[josedaniel-dev]

Summary

• fix invalid Compose containerfile keys to the standard dockerfile key
• align the dashboard container with its declared Node 22.12 minimum and use npm ci
• remove Podman bind mounts that hid image-built application artifacts on a clean checkout
• add a manual-only clean-runner quickstart smoke test

Root cause

Following the README literally failed before startup because Docker Compose rejected containerfile as an unknown build property. The dashboard image also used Node 20 despite the package declaring Node 22.12 or newer.

Smoke coverage

The manual workflow validates Compose, runs docker compose up -d, waits for the database-backed API and dashboard, sends a metadata-only synthetic trace, retrieves it, and always tears down volumes. It has no automatic trigger, avoiding recurring Actions consumption.

Verification

• Docker Compose configuration parse — passed
• Podman Compose file parsed with Docker Compose — passed
• actionlint 1.7.12 — passed
• git diff --check — passed
• Gitleaks staged scan — no findings
• hosted CI and one post-merge manual smoke run required