Refactored third party API detection to improve consistency

[Mrpopo911]

Description

Refactored third party API detection logic to remove duplication and improve consistency across scoring components.

Issue

Third party API detection logic was implemented in multiple places with slightly different conditions, leading to inconsistent behavior and maintainability issues as well as redundancy.

Fix

1. Introduced a helper function is_third_party_api
2. Replaced duplicate logic with a helper function

Impact

1. Ensures consistent detection of third-party API usage
2. Improves maintainability and readability
3. Reduces risk of scoring inconsistencies

[Stanzin7]

Thanks @Mrpopo911 — it would apply, but it edits dead code. api/scoring_legacy.py (the calculate_security_score / _calculate_permission_alignment_penalty functions) is explicitly retained only for backward-compat (see the module docstring, lines 3-8); the live scoring path is the V2 engine in scoring/engine.py. Refactoring the legacy module won't affect current behavior, so I'd recommend closing. If you're interested in scoring, the V2 engine in scoring/ is where new work lands.