v0.2.1: Change SHA256 input to file upload field

- Replace SHA256 text input with file upload field for checksum files
- Add readChecksumFile() JavaScript function using FileReader API
- Support .sha256 and .txt checksum file formats
- Add Promise-based async handling for file reading
- Add localized error messages for checksum file validation
- Update translations (de_CH) with new strings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.2.1] - 2026-01-22
+
+### Changed
+
+- SHA256 hash input changed from text field to file upload field
+- Checksum files (.sha256 or .txt) can now be uploaded directly
+- Improved user experience for version integrity verification
+
+### Technical Details
+
+- Added `readChecksumFile()` JavaScript function using FileReader API with Promise support
+- Checksum file format supports both "hash  filename" and plain "hash" formats
+- Added localized error messages for checksum file validation
+
 ## [0.2.0] - 2026-01-22
 
 ### Added