add composer-unused, comprehensive docs, and project restructure

- Add icanhazstring/composer-unused as dev dependency for dependency hygiene checks
- Add German documentation (docs/) covering architecture, conventions, workflows, and developer checklists
- Add API layer (ApiAuth, ApiBootstrap, ApiResponse), audit, scheduler, custom fields, and SSO services
- Add Microsoft OIDC SSO, API token management, and user lifecycle features
- Add swagger-ui vendor integration and OpenAPI spec
- Add production Docker setup and bin/ scripts
- Update composer dependencies, config, templates, and frontend assets throughout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -1,5 +1,4 @@
 APP_NAME=IMVS
-APP_SLOGAN=Immobilien Makler Verkaufs Software
 APP_URL=http://localhost:8080
 APP_ENV=dev
 APP_DEBUG=true
@@ -7,7 +6,10 @@ APP_TIMEZONE=Europe/Berlin
 APP_STORAGE_PATH=./storage
 APP_LOCALE=de
 APP_LOCALES=de,en
+APP_I18N_DOMAIN=default
+APP_CRYPTO_KEY=
 SESSION_NAME=IMVS
+TENANT_SCOPE_STRICT=true
 
 DB_HOST=db
 DB_PORT=3306
@@ -17,3 +19,17 @@ DB_PASS=imvs
 DB_ROOT_PASSWORD=imvs_root
 
 CACHE_SERVERS=memcached:11211
+
+FIREWALL_CONCURRENCY=10
+FIREWALL_SPINLOCK_SECONDS=0.15
+FIREWALL_INTERVAL_SECONDS=300
+FIREWALL_CACHE_PREFIX=fw_concurrency_
+FIREWALL_REVERSE_PROXY=false
+
+SMTP_HOST=smtp.example.com
+SMTP_PORT=587
+SMTP_USER=no-reply@example.com
+SMTP_PASS=
+SMTP_FROM=no-reply@example.com
+SMTP_FROM_NAME=IMVS
+SMTP_SECURE=tls