Python assertions are stripped when running with `python -O` (optimized
mode), making them unsuitable for runtime error handling.
1. `telegram_network.py:113` — After exhausting all fallback IPs, the code
uses `assert last_error is not None` before `raise last_error`. In
optimized mode, the assert is skipped; if `last_error` is unexpectedly
None, `raise None` produces a confusing `TypeError` instead of a
meaningful error. Replace with an explicit `if` check that raises
`RuntimeError` with a descriptive message.
2. `feishu.py:975` — The `_configure_with_overrides` closure uses
`assert original_configure is not None` as a guard. While the outer
scope only installs this closure when `original_configure` is not None,
the assert would silently disappear in optimized mode. Replace with an
explicit `if` check for defensive safety.
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