Add remote metrics setup

[vladiant]

Summary

This MR adds a remote observability setup so local Grafana/Prometheus can monitor a remotely hosted Commerce API (for example, Render), and adds an optional server-side Promtail agent for shipping remote Docker logs to Loki.

Motivation

The existing setup assumes the app and database run in the same local Docker Compose network.
When the app/database are remote, local observability was not directly usable.
This change introduces configurable remote scraping and remote log shipping paths.

Scope of Changes

Added

• .env.remote.example
• .env.server-logs.example
• docker-compose.remote.yml
• docker-compose.server-logs.yml
• observability/prometheus.remote.yml.tmpl
• observability/promtail.remote.yml.tmpl

Updated

• README.md

What’s Included

1) Remote metrics stack (docker-compose.remote.yml)

• Runs local observability services for remote targets:
• grafana
• prometheus
• loki
• tempo
• otel-collector
• Prometheus config is rendered from env vars at container startup.
• Supports HTTPS and custom metrics path through:
• REMOTE_SERVER_ADDRESS
• REMOTE_APP_SCHEME
• REMOTE_APP_PORT
• REMOTE_METRICS_PATH

2) Server-side remote log shipping (docker-compose.server-logs.yml)

• Adds a Promtail agent intended to run on the remote Docker host.
• Pushes logs to a configurable Loki endpoint.
• Uses:
• REMOTE_LOKI_PUSH_URL
• REMOTE_LOG_HOST
• REMOTE_LOG_JOB

3) Documentation updates (README.md)

• Added a full remote observability flow under Development Server Option B.
• Added a concrete Render example for:
• https://commercesystemdemo.onrender.com/
• Added quick verification commands and dashboard links.
• Documented remote limitations and server-side log shipping notes.
• Renumbered old local option to Option C.

Validation

• Verified remote endpoints on Render:
• / returns 200
• /health returns 200
• /metrics returns 200 with commerce_* metrics
• Verified compose rendering:
• docker compose -f docker-compose.remote.yml ... config
• docker compose -f docker-compose.server-logs.yml ... config
• Verified runtime behavior:
• Remote Prometheus target is up for commercesystemdemo.onrender.com:443
• Grafana is healthy and provisioned dashboards are available

How to Use (Render example)

cp .env.remote.example .env.remote