Build Stage 8 API v2 platform foundation

[anth-volk]

Summary

Implement Stage 8 of the unified API v2-alpha migration plan: establish the dormant v2 data and cache platform without cutting production traffic away from the existing API v1 owners.

Scope

• Provision and qualify a dedicated Supabase project used as direct Postgres and private object storage.
• Add a canonical SQLModel v2 schema with stable reports separated from versioned, independently rerunnable report runs.
• Add a distinct Postgres-only Alembic v2 chain, including autogenerated schema and data migrations, while leaving the v1 MySQL chain untouched.
• Replace writable runtime SQLite and per-container Redis with managed, shared Redis-backed cache repositories.
• Add Cloud Run, App Engine, CI, startup, lifecycle, cache-loss, and migration qualification coverage.
• Preserve Cloud SQL, Flask/API v1 routes, Simulation Entrypoint selection, compute routing, and public response contracts as the production authorities.

Acceptance criteria

• The Supabase v2 schema remains dormant during Stage 8.
• Durable domain data never uses Redis, and cache loss is recoverable as a miss.
• Production containers do not launch Redis or create a writable SQLite database.
• V2 report and report-run identifiers and rerun idempotency keys use native UUIDs.
• V1 MySQL migrations and existing API behavior remain unchanged.
• Focused unit, Postgres lifecycle, migration-contract, formatting, and lint checks pass.