docs: native Ubuntu install as primary; systemd and nginx

- install-ubuntu-24.04-native.md (production) and -docker.md (alternative)

- deploy/systemd/sac-api.service, nginx/sac.conf.example, env.native.example

- deployment, README, INDEX, work-plan, TZ updated

deploy/env.native.example

@@ -0,0 +1,19 @@
+# Native (systemd): скопировать в /etc/security-alert-center/sac-api.env
+# chmod 600 /etc/security-alert-center/sac-api.env
+# chown root:sac /etc/security-alert-center/sac-api.env
+
+DATABASE_URL=postgresql+psycopg2://sac:CHANGE_ME_POSTGRES_PASSWORD@127.0.0.1:5432/sac
+
+SAC_PUBLIC_URL=https://sac.example.com
+JWT_SECRET=CHANGE_ME_openssl_rand_hex_32
+
+# API key для агентов: Authorization: Bearer <ключ>
+# python3.12 -c "import secrets; print('sac_'+secrets.token_urlsafe(32))"
+SAC_BOOTSTRAP_API_KEY=sac_replace_with_generated_key
+
+EVENT_SCHEMA_PATH=/opt/security-alert-center/schemas/event-schema-v1.json
+
+SAC_ADMIN_USERNAME=admin
+SAC_ADMIN_PASSWORD=
+
+CORS_ORIGINS=*