[NO-JIRA] Fix HEIC file upload validation on Windows

[cloakedj]

Summary

Fix HEIC file upload validation on Windows browsers where the MIME type is not correctly reported. Added isWindows() utility function and enhanced HEIC input validation to fall back to file extension checking when MIME type is empty on Windows.

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Jira Ticket

Resolves: MWPW-NUMBER

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Test URLs

Env	URL
Before	https://main--da-express-milo--adobecom.aem.page/express/feature/image/convert/heic-to-jpg
After	https://heic-windows-fix--da-express-milo--adobecom.aem.page/express/feature/image/convert/heic-to-jpg?martech=off

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Verification Steps

1. Navigate to a HEIC conversion quick action page (e.g., /express/feature/image/convert/heic-to-jpg or /express/feature/image/convert/heic-to-png)
2. Upload a .heic file using the file picker or drag-and-drop
3. Before: On Windows, HEIC files may be rejected with "file type not supported" error because the browser reports an empty MIME type
4. After: HEIC files are correctly accepted on Windows by falling back to file extension validation

Test Scenarios

Scenario	Expected Behavior	Browser/OS
Upload .heic file via picker	File accepted, conversion starts	Chrome/Windows
Upload .heic file via drag-drop	File accepted, conversion starts	Chrome/Windows
Upload .heic file	File accepted (existing behavior)	Chrome/macOS
Upload .png/.jpg file	File accepted	Any
Upload unsupported file (.pdf)	Error shown	Any

Regression Test - Random Quick Actions

Validate that the following quick actions still work as expected after this change:

Quick Action	Test URL	File Type	Expected Behavior
Convert to JPG	https://heic-windows-fix--da-express-milo--adobecom.aem.page/express/feature/image/convert/jpg?martech=off	.png, .webp	File uploads and converts to JPG successfully
Resize Image	https://heic-windows-fix--da-express-milo--adobecom.aem.page/express/feature/image/resize?martech=off	.jpg, .png	File uploads and resize options appear
Convert to PNG	https://heic-windows-fix--da-express-milo--adobecom.aem.page/express/feature/image/convert/png?martech=off	.jpg, .webp	File uploads and converts to PNG successfully

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Potential Regressions

• https://heic-windows-fix--da-express-milo--adobecom.aem.live/express/feature/image/convert/heic-to-jpg?martech=off

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Commits

• 5fcac4a ✅ (latest)
• 5682892 ✅

[aem-code-sync]

	Page	Scores	Audits
📱	/express/feature/image/convert/heic-to-jpg?martech=off
🖥️	/express/feature/image/convert/heic-to-jpg?martech=off
📱	/express/feature/image/convert/heic-to-jpg?martech=off
🖥️	/express/feature/image/convert/heic-to-jpg?martech=off
📱	/express/feature/image/convert/jpg?martech=off
🖥️	/express/feature/image/convert/jpg?martech=off
📱	/express/feature/image/convert/png?martech=off
🖥️	/express/feature/image/convert/png?martech=off
📱	/express/feature/image/resize?martech=off
🖥️	/express/feature/image/resize?martech=off

[hadobe]

@cloakedj

I'm getting the "File not supported..." error when uploading the .heic file (Windows 11 / Chrome)

https://jira.corp.adobe.com/browse/MWPW-190912

[hadobe]

QE ticket.
https://jira.corp.adobe.com/browse/MWPW-190912

[nateyolles]

Waiting on @cloakedj for fixes