docs: update all documentation for email connector UI migration

- CLAUDE.md: add EmailConnectorService/Controller to vendor package
- .env.example: replace SMTP vars with note about runtime UI config
- docker/CLAUDE.md: update sign-in UI and bootstrap descriptions
- ui/CLAUDE.md: add EmailConfigPage, update sidebar and registration notes
- ui/sign-in/Dockerfile: update connector install comment
- installer: update README, .env.example (submodule)

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

CLAUDE.md

@@ -25,7 +25,7 @@ Agent-server protocol is defined in `cameleer/cameleer-common/PROTOCOL.md`. The
 |---------|---------|-------------|
 | `config/` | Security, tenant isolation, web config | `SecurityConfig`, `TenantIsolationInterceptor`, `TenantContext`, `PublicConfigController`, `MeController` |
 | `tenant/` | Tenant data model | `TenantEntity` (JPA: id, name, slug, tier, status, logto_org_id, db_password) |
-| `vendor/` | Vendor console (platform:admin) | `VendorTenantService`, `VendorTenantController`, `InfrastructureService` |
+| `vendor/` | Vendor console (platform:admin) | `VendorTenantService`, `VendorTenantController`, `InfrastructureService`, `EmailConnectorService`, `EmailConnectorController` |
 | `onboarding/` | Self-service sign-up onboarding | `OnboardingController`, `OnboardingService` |
 | `portal/` | Tenant admin portal (org-scoped) | `TenantPortalService`, `TenantPortalController` |
 | `provisioning/` | Pluggable tenant provisioning | `DockerTenantProvisioner`, `TenantDatabaseService`, `TenantDataCleanupService` |