fix: resolve startup crash from test import leak and silent retry data loss in invoke()

[xemishra]

Summary

This PR fixes two bugs: one that crashes the app before it opens, and one
that silently drops API data during retry attempts.

Bug 1 - Startup Crash: Test Mock Imported at Production Module Level

File: estimators/factory.py

MockUrlInvoker was imported unconditionally at the top of factory.py:

from tests.files.mocks import MockUrlInvoker

The tests/ package is not shipped in production installs or Docker images,
so this raises an ImportError the moment the app loads - before the window
even opens. No credentials are checked, no scan runs.

Fix: Deferred the import into get_mock_url_invoker() with a clear error
message explaining it is test-only. The factory now loads cleanly in all
environments.

---

Bug 2 - Silent Data Loss: Retry Logic Drops Requests in invoke()

File: util/connectors.py

Two issues in the invoke() retry loop:

1. Wrong source list for rebuild. curr_batch was filtered from itself
   on each iteration rather than from the original batch. Once a request
   was filtered out (due to an ID type mismatch), it could never re-enter
   the retry queue even if retries remained.

2. ID type mismatch. failed_response_ids was built as a plain list
   from response dicts whose "id" may be a string, while request["id"]
   is an int. The in check silently failed, so curr_batch became empty
   and all retries were skipped with no log warning.

3. Broken f-string. The failure logger used nested quotes incompatible
   with Python < 3.12, causing a SyntaxError and swallowing the exception
   path entirely.

Fix: Rebuilt curr_batch from the original batch list, used a set
of str-cast IDs for reliable membership testing, and corrected the logger
to safely format response IDs.

---

Testing

• Verified from estimators.factory import EstimatorFactory succeeds
  without the tests/ package present.
• Verified from util.connectors import UrlInvoker parses cleanly on
  Python 3.10+.

Files Changed

• estimators/factory.py
• util/connectors.py

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