refactor(form): improve _getUpload and remove unused getUploadedFileType

[amulet1]

• Separate upload handling from try/catch: file-not-uploaded logic
• Build $img as a local array and assign to $this->_img at the end, rather than mutating $this->_img piecemeal throughout the method
• Remove getUploadedFileType static method, inline/improve its logic
• Related code improvements

[TDannhauer]

Looks like a solid cleanup: clearer success vs. non-upload paths, single assignment into $this->_img['img'], and MIME handling after the file is moved to temp storage.

BC: getUploadedFileType was removed as a public static method. Is that intentional for FRAMEWORK_6_0? If anything outside this package still calls it, we should either keep a deprecated stub or document the break in the changelog / upgrade notes.

Tests: Could you add or extend tests for this flow (happy path upload, no new file with existing hash, explicit remove)? Even a small unit/integration test would help lock in behavior after this refactor.

[TDannhauer]

@ralflang what do you think about the BC break. is it okay?

[amulet1]

Note, the getUploadedFileType() was removed after I confirmed that it is not being used any other Horde modules.

In general, other places should rely on getImage() or getInfo() - and it looks like they do.