Improve IPv64 update performance and validation

[Ludy87]

Motivation

• Reduce latency and make updates more robust so the integration is faster and more user-friendly during startup and connectivity issues.
• Ensure domain input is validated strictly to avoid accidental acceptance of non-IPv64 zones.
• Improve user-facing behavior by restoring cached data on startup and clearing stale error notifications after successful updates.

Description

• Fetch account and domain information concurrently during coordinator refreshes using asyncio.gather() to reduce overall update time and race conditions (custom_components/ipv64/coordinator.py).
• Restore cached coordinator data at the start of _async_update_data() via a new _async_restore_cache() helper so sensors are available faster and during offline scenarios (custom_components/ipv64/coordinator.py).
• Convert get_domain() to return structured data and set explicit subdomains/error fields on failure for clearer downstream handling (custom_components/ipv64/coordinator.py).
• Add is_allowed_domain() in const.py and replace ad-hoc endswith() checks with this helper to accept only exact allowed zones or proper subdomains (custom_components/ipv64/const.py, custom_components/ipv64/config_flow.py, custom_components/ipv64/coordinator.py).
• Dismiss previous update-related persistent notifications on successful updates, clamp remaining-update counts to non-negative values, and use UTC timestamps for cache records to improve UX and correctness (custom_components/ipv64/coordinator.py).

Testing

• Ran ruff check custom_components/ipv64 and applied fixes, which completed successfully.
• Ran python -m compileall custom_components/ipv64 and verified all modules compiled without errors.
• Ran git diff --check to ensure no whitespace or diff issues; check passed.

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Codex Task

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Avoid issuing domain lookups on failed account retries

When the account-info request fails or is temporarily rate-limited, this gather has already started the get_domains request, and the outer retry loop then starts both calls again. Previously the domain lookup only ran after account info succeeded, so in a 429/5xx/timeout scenario on get_account_info each retry now burns an extra IPv64 API request (and get_domain has its own retries), which can quickly exceed the integration’s 3-requests/10s rate-limit handling and make transient failures worse. Fetch the domain data only after account info succeeds, or explicitly cancel/avoid the second task on retry.

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