fix(madara): properly parse srcset with image descriptors (w/x suffixes)

[IMXEren]

Refactored getSrcSetImage() to correctly handle comma-separated srcset entries with width (w) and pixel-density (x) descriptors. Previously the method used to compare URLs lexicographically, which breaks on srcset="link-34x68.jpg 34w, link-330x700.jpg 330w" and chooses link-34x68.jpg.

Adds IMAGE_DESCRIPTOR_REGEX companion constant and prefers highest-resolution images by descriptor value, falling back to lexicographical URL comparison when no descriptors are present.

Checklist:

• Updated versionCode value in build.gradle.kts
• Updated baseVersionCode in build.gradle.kts (if updated multisrc theme code)
• Referenced all related issues in the PR body (e.g. "Closes #xyz")
• Set the contentWarning configuration in build.gradle.kts appropriately
• Have not changed source names
• Have explicitly kept the id if a source's name or language were changed
• Have tested the modifications by compiling and running the extension through Android Studio
• Have removed web_hi_res_512.png when adding a new extension
• This PR is AI-assisted, I have reviewed the changes manually and confirmed they are not slop

[IMXEren]

Hey @vetleledaal, just checking in to see if everything looks good here or if anything is missing.

Thanks!

[vetleledaal]

Need additional consideration when making changes to Madara as it will update a lot of extensions (approx. 300).

I made something similar in the past, but it was specific to that one source (via #9815):

extensions-source/src/tr/jiangzaitoon/src/eu/kanade/tachiyomi/extension/tr/jiangzaitoon/Jiangzaitoon.kt

Lines 26 to 47 in a4b215a

	override fun String.getSrcSetImage(): String? {
	/* Assumption: URL is absolute
	* Assumption: descriptor is always in width
	*/
	return this
	.split(",")
	.mapNotNull { candidate ->
	candidate
	.trim()
	.split(" ", limit = 2)
	.takeIf { it.size == 2 }
	?.let { (url, desc) ->
	desc
	.takeIf { it.endsWith("w") }
	?.removeSuffix("w")
	?.toIntOrNull()
	?.let { size -> url to size }
	}
	}
	.maxByOrNull { it.second }
	?.first
	}

[vetleledaal]

Move the class to avoid recompilation of invariant regex.