feat(media): Add comprehensive logging for media uploads - v1.4.1

Implements media upload logging per docs/design/v1.4.1/media-logging-design.md

Changes:
- Add logging to save_media() in starpunk/media.py:
  * INFO: Successful uploads with file details
  * WARNING: Validation/optimization/variant failures
  * ERROR: Unexpected system errors
- Remove duplicate logging in Micropub media endpoint
- Add 5 comprehensive logging tests in TestMediaLogging class
- Bump version to 1.4.1
- Update CHANGELOG.md

All media upload operations now logged for debugging and observability.
Validation errors, optimization failures, and variant generation issues
are tracked at appropriate log levels. Original functionality unchanged.

Test results: 28/28 media tests pass, 5 new logging tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

starpunk/routes/micropub.py

@@ -199,5 +199,4 @@ def media_endpoint():
         return error_response("invalid_request", str(e), 400)
 
     except Exception as e:
-        current_app.logger.error(f"Media upload failed: {e}")
         return error_response("server_error", "Failed to process upload", 500)