Integrate new leaderboard

[HactarCE]

I am happy to take over any of the @milojacquet tasks if Milo is present to give me guidance.

For existing speedsolves

• Make it possible to compile hsc-leaderboard locally without Postgres. This can happen either (or both) of two ways:
  • Switch from Postgres to SQLite (preferred) (@milojacquet)
  • Run cargo install sqlx-cli and then cargo sqlx prepare whenever the schema changes during development (@milojacquet)
• Run leaderboard onto the cloud.hypercubing.xyz server, set up Discord bot, test end-to-end (@HactarCE)
• Populate database from latest solves.csv (@milojacquet)
• Update hypercubing.xyz (@HactarCE or others)

For FMC / HSC2 integration

• FMC support in database / web UI (@milojacquet)
• Automatic FMC verification ( + @milojacquet)
  • hyperpuzzle::verify() (@HactarCE)
  • Integration into leaderboard server (@milojacquet)
    • Timeout on puzzles that are too big (fallback to manual verification for now?)

These are basically required before an HSC2 public prerelease because we want to track FMC records for all puzzles people have been solved.

Possible future work

• Have the leaderboard server send a seed to the client, and verify that the solve was completed within some reasonable time window.