Bug: ActivityPub processing fails with `as:Public` and string `to`/`cc`

[ruine0213]

Describe the bug
Mbin fails to process some ActivityPub objects containing as:Public or string to / cc fields.
This results in inbox processing errors and posts not being imported.

On which Mbin instance did you find the bug?
bin.pivox.net

Which Mbin version was running on the instance?
1.10.0rc1

To Reproduce
Steps to reproduce the behavior:

1. Follow or fetch a post from Ghost CMS or PeerTube
2. Or receive a boost via Mastodon
3. Try to view or import the post in Mbin
4. See error in logs / inbox processing fails

Expected behavior
Posts should be imported correctly.
to / cc should support both string and array formats, and as:Public should not be treated as a resolvable actor.

Screenshots
N/A (log-based issue)

Desktop (please complete the following information):

• OS: OS: Ubuntu24.04LTS
• Browser: Firefox
• Browser Version: 149

Additional context
Errors observed:

WebFinger handle is malformed 'as:Public'

Cannot access offset of type string on string