[scheduler] Add end-to-end stress tests to scheduler

[DiegoTavares]

Booking + accounting stress suite for the Rust scheduler.
cluster feed → job query → host matching → dispatch) against a realistic farm in
two phases inside one process:

1. drain — farm capacity comfortably exceeds demand. Benchmarks booking
   throughput (frames/s over the active booking window) and requires ≥90%
   (STRESS_DRAIN_TARGET) of frames to dispatch.
2. saturation — demand vastly exceeds tight subscription bursts and per-job
   core caps, so the Redis Lua cap check becomes the binding constraint. Verifies
   enforcement (no booking above burst / job max-cores) and that rejections
   actually flowed through the accounting hot path.
   After each phase, an audit cross-checks every Redis acct:* hash against
   SUM(proc) in Postgres plus host/frame/stat invariants — with the recompute and
   limit-reseed loops pushed beyond the test horizon, agreement proves the dispatch
   hot path (Lua book + force-rollback) kept accounting exact on its own.

Requirements

• Postgres with migrations applied, from the repo root: docker compose up -d flyway
• A Docker daemon (the suite starts a throwaway Redis container via testcontainers;
  all Redis state dies with the container)

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