Fix Set charset to UTF-8 in convertMailQueryToHordeQuery

[taiebot]

Potentially Fix
bugs #9257 #10572

This is entirely AI generated but in 9257 there was a POC.

I have "partially" tested this it works i do not get the error that i get on #10572 with this search "identité" and "réunion" i must have an other problem with my yahoo mailbox because email bodies do not get downloaded (testing on main branch)

AI suggested to do it here
Ai slop below ...

Why this works

$query is created once

UTF‑8 is set once

The same $query object is passed through all tokens

No duplication

No crashes

Horde correctly converts UTF‑8 → IMAP UTF‑7 internally 

[github-actions]

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