fix: forward idempotency_key, ignore_ssl_errors and do_not_retry in ad-hoc webhooks

[vdusek]

Description

• Webhook fields idempotency_key, ignore_ssl_errors and do_not_retry were silently dropped when the webhook was passed as an ad-hoc webhook to Actor.start() / Actor.call() / Actor.call_task(), while the class docstring advertises that usage.
• The platform accepts and honors all three for ad-hoc webhooks (verified in apify-core); the drop happened only because the client's WebhookRepresentation model declared just the four templating fields. to_client_representations now forwards all Webhook fields.
• Depends on fix: add idempotency_key, ignore_ssl_errors and do_not_retry to WebhookRepresentation apify-client-python#854 (which in turn builds on fix(openapi): add missing ad-hoc webhook fields to WebhookRepresentation apify-docs#2640). Before marking ready: bump the apify-client pin to >=3.0.3 and update uv.lock once the client release is out — CI is expected red until then.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.95%. Comparing base (a87e8d1) to head (d4c544e).
⚠️ Report is 5 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (a87e8d1) and HEAD (d4c544e). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (a87e8d1)	HEAD (d4c544e)
unit	1	0
e2e	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #963       +/-   ##
===========================================
- Coverage   90.00%   56.95%   -33.06%     
===========================================
  Files          49       49               
  Lines        3053     3085       +32     
===========================================
- Hits         2748     1757      -991     
- Misses        305     1328     +1023     

Flag	Coverage Δ
e2e	?
integration	56.95% <ø> (+0.09%)	⬆️
unit	?

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