Asura Scans: Format comma separated alt titles

[prem-k-r]

Regression: reverted from alternativeTitles back to alt_titles (Related #17626 )
1. alternativeTitles is blank for some series, unlike alt_titles — e.g. "A Painter Who Draws Dungeons" or "Got Dropped into a Ghost Story, Still Gotta Work".
2. alternativeTitles uses comma as separator for some series — e.g. "Sword of the Undying", "The Forgotten Field" or "Only I Have an EX-Grade Summon" and many more. Comma can be part of a title, whereas alt_titles uses newline or • only.

Nvm, just noticed switched from REST API to Astro props

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 running the extension
• 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