labelle.games v2: Cloud API (upload, versioning, tester management)

[apotema]

Part of #139 (labelle.games platform).

Scope

Backend API server for labelle.games:

• POST /api/deploy — receive APK upload from CLI, store in blob storage
• GET /api/update/<project>/<channel> — companion app polls for new versions
• POST /api/testers — add/remove testers
• GET /api/projects/<id>/status — version history, download counts

Auth

• GitHub OAuth for developers (login via CLI)
• Email/magic-link for testers (no account needed)

Storage

• S3-compatible blob store for APKs (R2/S3/GCS)
• Postgres for projects, testers, versions, channels

Channels

• internal (default), staging, production

Tech decisions (TBD)

• Language: Go / Rust / Node
• Hosting: Fly.io / Railway / VPS
• Domain: labelle.games

[apotema]

Deferred to v2 per the pivot proposed in #139 (Obtainium + GitHub Releases for v1). The cloud API (upload, versioning, tester management) becomes relevant once we outgrow Obtainium's self-serve subscription model — see #139 for the v2 triggers. Leaving this open as the v2 spec.