[FEAT] Implement Basic Service

[bbengfort]

Scope of changes

Implements the basic service architecture in Golang.

Estimated PR Size:

• Tiny
• Small
• Medium
• Large
• Huge

Acceptance criteria

This PR will be merged without review.

Author checklist

• I have manually tested the change and/or added automation in the form of unit tests or integration tests
• I have updated the dependencies list
• I have added new test fixtures as needed to support added tests
• I have added or updated the documentation
• I have run go generate to update generated code

---

Note

Medium Risk
Introduces a new Gin-based HTTP server with health/status endpoints, maintenance gating, and content negotiation, plus new dependencies and startup/shutdown behavior. Risk is moderate because it establishes core runtime/service behavior but doesn’t touch auth or persistent data.

Overview
Implements the initial runnable uptime service: a CLI (serve, config) that loads env via godotenv, prints config usage, and starts the server.

Adds a Gin-based HTTP server with graceful shutdown, Kubernetes probe endpoints (/healthz, /livez, /readyz), a public GET /v1/status heartbeat returning status/uptime/version, and optional global maintenance mode that returns 503 with JSON/HTML negotiation.

Introduces config loading via confire, standard JSON API reply/error helpers, HTML scene context for error pages, and an .air.toml dev hot-reload build setup; updates go.mod/go.sum with required server/telemetry dependencies.

^{Written by Cursor Bugbot for commit f1b33a7. Configure here.}