fix: implement exponential backoff retry for transient network errors

[Bedirhan3428]

Description

This PR enhances the reliability of the lago-python-client network layer by introducing transient network and server-side error resilience with an Exponential Backoff retry mechanism inside services/request.py.

Why is this necessary?

Currently, the _create_retry_wrapper specifically handles HTTP 429 (Rate Limit) errors. However, if a transient network anomaly occurs (such as a temporary socket dropping, DNS timeout, or edge proxies returning 502 Bad Gateway, 503 Service Unavailable, or 504 Gateway Timeout), the SDK crashes instantly. For critical production telemetry and financial invoicing, these temporary drops should be safely handled with immediate, non-blocking exponential retries before giving up.

What changes were made?

1. Transient Server Errors Hook: Explicitly caught status codes 502, 503, and 504, raising a properly formed httpx.HTTPStatusError.
2. Exponential Backoff Isolation: Wrapped the underlying network executions in a try/except block to catch httpx.RequestError and httpx.TimeoutException alongside server failures.
3. Resiliency Loop: Implemented a max-retry limit of 3 network attempts, starting with a base delay of 1.0s and doubling sequentially (1s -> 2s -> 4s) using time.sleep().
4. State Preservation: Synchronized both network_retry_attempt and the pre-existing SDK retry_attempt state to maintain absolute tracking accuracy for subsequent observability steps (emit_rate_limit_info).
5. No Breaking Changes: Left the original HTTP 429 workflow completely intact.

Tested locally against the entire test suite, running flawlessly with 414 tests passing.

[cla-check-bot]

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[cla-check-bot]

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