feat: Private Tracker Style invites

.gitea/workflows/release.yaml

.gitea/workflows/test.yaml

.gitlab-ci.yml

.gitlab/issue_templates/file-upload-error.md

.vscode/settings.json

Cargo.lock

Cargo.toml

README.md

config.sample.toml

docs/API.md

docs/DB.md

docs/benchmarks.md

docs/docker-compose.yaml

docs/engines.md

docs/expiry mockup.png

docs/info.md

schema.sql

src/config.rs

src/db.rs

src/db_tests.rs