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

Task #534 — backend, infra, and tooling only. UI ships in Stage 2.

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.
- Zod validation, bcrypt hashing, in-memory rate limiter for 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. The web service no longer
  publishes a port directly — Caddy is the only public ingress.
- docker/Caddyfile: HTTPS site for LOCAL_DOMAIN/LOCAL_IP with
  WebSocket upgrade preserved and a plaintext :80 fallback when
  HTTPS_MODE=skip (dev-only).
- .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).
  start.sh untouched.

Tests
- artifacts/api-server/tests/setup-wizard.test.mjs: 7/7 pass
  (snapshot/restore admin role + system_settings around tests).
- scripts/tests/local-setup.test.mjs: 2/2 pass (first-run bootstrap
  + second-run no-op idempotency with mkcert/openssl stubs).

Constraints honored: no force-push, no destructive ops, start.sh
preserved, 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.

lib/db/src/schema/settings.ts

@@ -17,3 +17,23 @@ export const updateAppSettingsSchema = createInsertSchema(appSettingsTable)
   .partial();
 export type AppSettings = typeof appSettingsTable.$inferSelect;
 export type UpdateAppSettings = z.infer<typeof updateAppSettingsSchema>;
+
+// ---------------------------------------------------------------------------
+// system_settings — single-row install-state record consumed by the
+// First-Time Setup Wizard. Distinct from `app_settings` (which holds
+// admin-editable site config). The row id is always 1; the wizard upserts
+// it once during /api/setup/complete and never deletes it.
+// ---------------------------------------------------------------------------
+export const systemSettingsTable = pgTable("system_settings", {
+  id: integer("id").primaryKey().default(1),
+  installed: boolean("installed").notNull().default(false),
+  installedAt: timestamp("installed_at", { withTimezone: true }),
+  baseUrl: varchar("base_url", { length: 500 }),
+  localDomain: varchar("local_domain", { length: 200 }),
+  localIp: varchar("local_ip", { length: 64 }),
+  httpsMode: varchar("https_mode", { length: 16 }).notNull().default("local"),
+  appVersion: varchar("app_version", { length: 64 }),
+  updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow().$onUpdate(() => new Date()),
+});
+
+export type SystemSettings = typeof systemSettingsTable.$inferSelect;