feat: self-service sign-up with email verification and onboarding

Complete sign-up pipeline: email registration via Logto Experience API,
SMTP email verification, and self-service trial tenant creation.

Layer 1 — Logto config:
- Bootstrap Phase 8b: SMTP email connector with branded HTML templates
- Bootstrap Phase 8c: enable SignInAndRegister (email+password sign-up)
- Dockerfile installs official Logto connectors (ensures SMTP available)
- SMTP env vars in docker-compose, installer templates, .env.example

Layer 2 — Experience API (ui/sign-in/experience-api.ts):
- Registration flow: initRegistration → sendVerificationCode → verifyCode
  → addProfile (password) → identifyUser → submit
- Sign-in auto-detects email vs username identifier

Layer 3 — Custom sign-in UI (ui/sign-in/SignInPage.tsx):
- Three-mode state machine: signIn / register / verifyCode
- Reads first_screen=register from URL query params
- Toggle links between sign-in and register views

Layer 4 — Post-registration onboarding:
- OnboardingService: reuses VendorTenantService.createAndProvision(),
  adds calling user to Logto org as owner, enforces one trial per user
- OnboardingController: POST /api/onboarding/tenant (authenticated only)
- OnboardingPage.tsx: org name + auto-slug form
- LandingRedirect: detects zero orgs → redirects to /onboarding
- RegisterPage.tsx: /platform/register initiates OIDC with firstScreen

Installers (install.sh + install.ps1):
- Both prompt for SMTP config in SaaS mode
- CLI args, env var capture, cameleer.conf persistence

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -79,6 +79,12 @@ services:
       PG_DB_SAAS: ${POSTGRES_DB:-cameleer_saas}
       SAAS_ADMIN_USER: ${SAAS_ADMIN_USER:-admin}
       SAAS_ADMIN_PASS: ${SAAS_ADMIN_PASS:-admin}
+      # SMTP (for email verification during registration)
+      SMTP_HOST: ${SMTP_HOST:-}
+      SMTP_PORT: ${SMTP_PORT:-587}
+      SMTP_USER: ${SMTP_USER:-}
+      SMTP_PASS: ${SMTP_PASS:-}
+      SMTP_FROM_EMAIL: ${SMTP_FROM_EMAIL:-noreply@cameleer.io}
     healthcheck:
       test: ["CMD-SHELL", "node -e \"require('http').get('http://localhost:3001/oidc/.well-known/openid-configuration', r => process.exit(r.statusCode === 200 ? 0 : 1)).on('error', () => process.exit(1))\" && test -f /data/logto-bootstrap.json"]
       interval: 10s