feat(server): support installable license (#12181)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Added support for installing self-hosted team licenses via encrypted license files.
  - Introduced a new "Onetime" license variant for self-hosted environments.
  - Added a GraphQL mutation to upload and install license files.
  - License details now display the license variant.

- **Bug Fixes**
  - Improved error messages for license activation and expiration, including dynamic reasons.

- **Localization**
  - Updated and improved license-related error messages for better clarity.

- **Tests**
  - Added comprehensive end-to-end tests for license installation scenarios.

- **Chores**
  - Enhanced environment variable handling and public key management for license verification.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/migrations/20250508073308_installable_license/migration.sql

@@ -0,0 +1,3 @@
+-- AlterTable
+ALTER TABLE "installed_licenses" ADD COLUMN     "license" BYTEA,
+ADD COLUMN     "variant" VARCHAR;