refactor: remove obsolete resource download and installer endpoints

- Deleted the `POST /resources/get/{dataFolder?}` and `GET /resources/get-installer` endpoints as part of the architectural shift towards simplified resource management.
- Removed associated methods and configurations, including `ResourcesService.GetEncryptedResource`, `ResourcesService.GetInstaller`, and related properties in `ResourcesConfig`.
- Cleaned up environment variables and configuration files to reflect the removal of installer-related settings.
- Eliminated the `GetResourceRequest` DTO and its validator, along with the `WrongResourceName` error code.
- Updated documentation to clarify the changes in resource handling and the retirement of per-user file encryption.

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

@@ -22,8 +22,6 @@ ASPNETCORE_JwtConfig__TokenLifetimeHours=4
 
 # ---------- Resource storage (filesystem) -----------------------------------
 ASPNETCORE_ResourcesConfig__ResourcesFolder=Content
-ASPNETCORE_ResourcesConfig__SuiteInstallerFolder=suite
-ASPNETCORE_ResourcesConfig__SuiteStageInstallerFolder=suite-stage
 
 # ---------- Container build / image label ------------------------------------
 # Injected at build time as --build-arg CI_COMMIT_SHA=… by Woodpecker.