feat(setup): first-run wizard — admin, GitHub App, tunnel, done (#71)

* feat(setup): first-run wizard — admin, GitHub App, tunnel, done

- GET /api/v1/setup/status (public): has_users, needs_setup,
  has_github_app, has_tunnel. app_settings.setup_completed flag; installs
  with existing projects auto-complete so upgrades never see the wizard.
- POST /api/v1/setup/complete records the flag.
- /setup page: progress rail + four steps — create admin (links into the
  bootstrap sign-up with redirect back), GitHub App manifest flow,
  optional Cloudflare tunnel token, finish. Every optional step is
  skippable; nothing blocks.
- PlatformShell redirects signed-in users to /setup while needs_setup.
- The GitHub App callback honors a sessionStorage return marker set by
  the wizard so provisioning resumes at /setup instead of /settings.
- OpenAPI documents both endpoints.

Verified live: status reports auto-completed on this install,
complete persists the flag, response shape matches the client.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* test(setup): wizard step-state coverage

Five cases across the state machine: fresh-install account prompt,
sign-in resume, git-provider step, tunnel step, and finish.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ROADMAP2.md

@@ -537,8 +537,12 @@ and wired refs, one click or one CLI call.
 - [ ] **sqlc port** — ~140 raw `database/sql` sites → `sqlc/queries/`.
 - [ ] **Tests** — canvas/wizard frontend coverage, deployment/template/
   webhook table tests, Playwright e2e golden path.
-- [ ] **First-run wizard** — admin → GitHub App (manifest flow from
-  Phase G makes this self-serve) → Tunnel → done.
+- [x] **First-run wizard** — public `GET /setup/status` + authed
+  `POST /setup/complete`; `/setup` page steps admin account → GitHub App
+  manifest flow (callback returns to the wizard via a session marker) →
+  optional Cloudflare tunnel token → done. Shell redirects signed-in
+  users to `/setup` while `needs_setup`; installs with existing projects
+  auto-complete so nobody gets nagged retroactively.
 - [ ] **Self-upgrade loop verification**, docs freshness, v1.0.0 release.
 
 ## 11. Deliberately not imported from dflow