fix(zammad): handle flat list response from search API

[skjnldsv]

Summary

Newer Zammad instances return a flat list of ticket objects from the
search endpoint instead of the {"assets": {"Ticket": {...}}} enveloppe.

Fix

Detect the response type:

• list → build {str(id): ticket} dict directly
• dict → existing assets.Ticket unwrap path

Both paths produce the same structure consumed by TicketsUpdated.fetch().

Traceback

Traceback (most recent call last):
  ...
  File ".../did/plugins/zammad.py", line 114, in fetch
    for _, ticket in self.parent.zammad.search(query).items():
                     ~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File ".../did/plugins/zammad.py", line 63, in search
    result = self.perform_search(query)["assets"]
             ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
TypeError: list indices must be integers or slices, not str

Tested against a Zammad instance runing the newer API format, confirmed working.

[skjnldsv]

cc @come-nc