F2.1c — Add the local Hono server health skeleton

[Flow-Fly]

Parent: #133. Grandparent: #132 / #72. Depends on: #270 and #266.

Goal

Add the smallest locally runnable server process: typed configuration, one health route, graceful startup/shutdown, and focused tests.

Scope

• Add the owner-approved server/ workspace.
• Add the Hono app and Node entrypoint.
• Add typed environment parsing for process-level configuration only.
• Add GET /api/health reporting process and build/version health; database and storage adapters remain explicitly unavailable until later slices.
• Add local development scripts and server tests.
• Add CORS configuration for the documented client origin without deploying anything.

Out of scope

• No Postgres, Drizzle, S3, MinIO, auth, sync routes, Docker, or cloud deployment.
• No client account or sync UI.

Acceptance

• A fresh clone can install dependencies and start the client and local server.
• The health route is deterministic and tested.
• Missing or invalid required environment values fail with a clear startup error.
• Existing client checks remain green.

Risk and routing

Risk: low after dependencies land.
Worker-ready: no; keep queued until the ADR and shared contract are approved and merged.