TDK high-score service

This small Axum service stores the shared top-ten table in SQLite. It exposes:

GET  /healthz
GET  /api/highscores
POST /api/highscores

The POST body is JSON with a 21-character maximum name and a u32 score. The response is the canonical top-ten JSON array.

A newly created database starts with the original distributed demo table. An existing database, including an existing empty database, is left unchanged.

Submissions are anonymous and intentionally trust the browser's score. Add rate limiting, moderation, or server-side run verification if the table needs to resist forged scores.

Run it from tdkpin-rs with:

TDKPIN_HIGHSCORE_BIND=127.0.0.1:3000 \
TDKPIN_HIGHSCORE_DB=/var/lib/tdkpin/highscores.sqlite3 \
cargo run --manifest-path highscore-server/Cargo.toml

Copy the rate and connection zone declarations from nginx.conf.example into the existing http block, then place its two location blocks inside the public site's server block. The example bounds per-client and aggregate API traffic, request bodies, and proxy waits. The browser client expects the API at /api/highscores on the same origin as the game.

The crate inherits the parent rustfmt.toml; run just fmt-highscore-server when formatting it directly.