refactor(cronjobs): migrate mass_scanners, firehol, and spamhaus_drop to HttpClient.

[Prasad8830]

Description

This PR handles the second batch of standardising our cron jobs HTTP fetchers, as discussed in #1214.

It migrates the mass_scanners, firehol, and spamhaus_drop endpoints to utilise the new centralised HttpClient wrapper introduced in #1253. This refactor replaces ad-hoc requests.get calls with the shared client, ensuring standardised error handling, built-in logging, and automatic retries for server errors.

For firehol and spamhaus_drop, the original explicit timeout=60 argument was intentionally preserved to prevent large blocklist fetches from failing due to premature timeouts.

Related issues

• Refs Standardize cronjob HTTP fetchers with a shared client wrapper #1214
• Depends on feat(cronjobs): add shared HTTP client wrapper. Refs #1214 #1253, refactor(cronjobs): migrate tor_exit_nodes and whatsmyip to HttpClient. Refs #1214 #1254

Type of change

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Chore (refactoring, dependency updates, CI/CD changes, code cleanup, docs-only changes).

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