feat(setup): Stage 1 first-time setup wizard backend (no UI)

Task #534 — backend, infra, tooling. UI ships in Stage 2 (#535).

Backend
- New system_settings table (id=1 singleton): installed flag, base_url,
  local_domain, local_ip, https_mode, app_version. Pushed to dev DB.
- New /api/setup/status (open) and /api/setup/{validate,complete}
  (gated by requireSetupOpen — 409 once installed).
- completeInstall is fully transactional: pg_advisory_xact_lock
  serializes concurrent callers, double-gates on installed flag and
  admin existence, then atomically creates the admin user, assigns
  admin role + Admins/Everyone groups, and flips system_settings to
  installed=true. Rolls back on any failure.
- Added redirectIfSetupNeeded() helper returning the full SetupStatus
  payload alongside a redirect target for SPA routing decisions.
- Zod validation, bcrypt hashing, in-memory rate limiter on the
  setup endpoints.

Backward compat
- scripts/src/seed.ts now branches on installed flag + admin
  existence + SEED_*_PASSWORD env vars. Legacy installs (admin
  exists, system_settings empty) get backfilled to installed=true
  via ON CONFLICT DO UPDATE so they are never forced through the
  wizard. When env passwords are unset and no admin exists, the
  seed prints a wizard hint instead of seeding.

Infra
- docker-compose.yml: replaced nginx edge with a Caddy service that
  mounts ./certs and ./docker/Caddyfile{,.skip}. The web service no
  longer publishes a port directly — Caddy is the only public ingress.
- Caddy entrypoint picks Caddyfile.skip (HTTP-only, no certs) when
  HTTPS_MODE=skip so a fresh host without mkcert can still boot.
- docker/Caddyfile: HTTPS site for LOCAL_DOMAIN/LOCAL_IP with
  WebSocket upgrade preserved and an HTTP→HTTPS redirect.
- start.sh: preserved. Now auto-picks HTTPS_MODE=skip when no cert
  is on disk and maps Caddy's HTTP_PORT to APP_PORT in skip mode so
  the legacy http://localhost:${APP_PORT} URL keeps working. In
  local/byo mode it prints the https://${LOCAL_DOMAIN} URL.
- .env.example: added LOCAL_DOMAIN, LOCAL_IP, BASE_URL, HTTP_PORT,
  HTTPS_PORT, HTTPS_MODE; SEED_*_PASSWORD now optional.

Tooling
- scripts/local-setup.sh: idempotent OS-aware bootstrap (.env upsert,
  mkcert hint, cert SAN check, dry-run via LOCAL_SETUP_DRY_RUN).

Tests
- artifacts/api-server/tests/setup-wizard.test.mjs: 7/7 pass.
- scripts/tests/local-setup.test.mjs: 2/2 pass.

Constraints honored: no force-push, no destructive ops, start.sh
preserved & still works, scripts idempotent, volumes/DB never
touched, HTTPS skip mode dev-only, wizard does not edit
LOCAL_DOMAIN/LOCAL_IP.

Out of scope / not addressed: pre-existing TS errors in
routes/users.ts and pre-existing failure in
executive-meetings-postpone-race.test.mjs.

artifacts/api-server/src/lib/setupRateLimit.ts

@@ -32,6 +32,7 @@ function jsonHandler(_req: Request, res: Response): void {
 
 // Stricter than the generic auth limiter — first-time setup is a one-shot
 // flow, so we cap any single IP to a small handful of POSTs per window.
+// Applied only to /setup/validate and /setup/complete (mutation endpoints).
 export const setupRateLimit: RateLimitRequestHandler = rateLimit({
   windowMs: envInt("SETUP_RATE_LIMIT_WINDOW_MS", 15 * 60_000),
   max: envInt("SETUP_RATE_LIMIT_MAX", 10),
@@ -40,3 +41,15 @@ export const setupRateLimit: RateLimitRequestHandler = rateLimit({
   skip: skipForLocalDev,
   handler: jsonHandler,
 });
+
+// Looser limiter for GET /setup/status. The SPA polls this on every
+// route change to decide whether to redirect to the wizard, so it
+// must tolerate normal user navigation without locking anyone out.
+export const setupStatusRateLimit: RateLimitRequestHandler = rateLimit({
+  windowMs: envInt("SETUP_STATUS_RATE_LIMIT_WINDOW_MS", 60_000),
+  max: envInt("SETUP_STATUS_RATE_LIMIT_MAX", 120),
+  standardHeaders: true,
+  legacyHeaders: false,
+  skip: skipForLocalDev,
+  handler: jsonHandler,
+});

artifacts/api-server/src/routes/setup.ts

@@ -1,5 +1,5 @@
 import { Router, type IRouter } from "express";
-import { setupRateLimit } from "../lib/setupRateLimit";
+import { setupRateLimit, setupStatusRateLimit } from "../lib/setupRateLimit";
 import { requireSetupOpen } from "../middlewares/setupGate";
 import {
   readStatus,
@@ -12,7 +12,7 @@ const router: IRouter = Router();
 
 // Status is read-only and must remain reachable AFTER install too, so the
 // SPA can decide routing. It is rate-limited but NOT gated.
-router.get("/setup/status", setupRateLimit, async (_req, res, next) => {
+router.get("/setup/status", setupStatusRateLimit, async (_req, res, next) => {
   try {
     const status = await readStatus();
     res.json(status);