v0.1.0

First working slice: authenticate, submit Python code, poll for the result —
sandboxed, metered by tenant, with signed completion webhooks.

Added

• Multi-tenant auth: POST /auth/register, /auth/login, /auth/refresh
  with bcrypt passwords, JWT access/refresh pairs, and tenants[] claims.
  Register auto-provisions a personal tenant (owner) in one transaction.
• Executions API: POST /executions (submit, 202 {id, status: queued}),
  GET /executions (paged list), GET /executions/{id} (status, stdout,
  stderr, exit code). Tenant-scoped; cross-tenant reads return 404.
• Tenants API: POST /tenants (org tenant, caller becomes owner),
  GET /tenants/{id}. Path id must equal X-Tenant-ID.
• NATS JetStream pipeline: durable EXEC_SUBMIT / EXEC_RESULT streams;
  gateway publishes exec.submit.<lang>; queue failure marks the row
  failed and returns 502.
• Dispatcher execution loop: durable pull consumer, conditional
  queued → running claim (duplicates acked, never re-run), one sandbox
  container per execution (gVisor runsc, non-root, no network, read-only
  rootfs, 128 MB / 0.5 CPU / 32 pids, 1–60 s timeout), result write-back
  plus exec.result.<id> summary.
• Signed webhooks: webhook_url on submissions, HMAC-SHA256 delivery with
  retries, SSRF guard at submit and delivery time; 503 when no signing
  secret is configured.
• Sandboxes: stale-running reaper, OOM detection, 64 KiB output
  truncation, boot-time leftover-container sweep.
• Runner image: runner/docker (python:3.12-slim, numeric nobody user).
• Postgres schema with embedded idempotent migrations (auto-applied at
  startup) and sqlc-generated queries; live /readyz checks.
• Compose stack (postgres:16, nats:2, gateway, dispatcher), CI
  (vet + race + lint + build), OpenAPI spec, webhook signing docs.

Fixed

• Tenant creation slug-conflict retry aborted the whole transaction
  (25P02); retries now run in per-attempt savepoints (register and
  org-tenant creation).