Investigate and fix severity-to-priority mapping for enterprise repositories

### Feature Description

Investigate why severity-to-priority mapping works for AbsaOSS-to-AbsaOSS repositories but fails for enterprise repositories, and provide a fix or a documented workaround.

### Problem / Opportunity

The GraphQL call used for severity-to-priority mapping fails on enterprise repositories with:

```
WARNING - GraphQL call failed: gh: Resource protected by organization SAML enforcement. You must grant your Personal Access token access to this organization.
```

This blocks adoption of the workflow for enterprise-protected repositories.

### Acceptance Criteria

1. Root cause of the SAML enforcement failure is identified and documented.
2. Either a fix is implemented that supports enterprise repositories, OR
3. An alternative solution is provided: a standalone mapping script where users supply their own SAML-authorized token and target API endpoint.
4. The workaround/solution is documented in the repository.

### Proposed Solution

Investigate whether the GraphQL query can be adapted to pass a user-supplied token scoped to the enterprise org.
As an alternative, provide a standalone Python/shell script that accepts `--token` and `--api-url` parameters for mapping severity to priority without relying on the shared workflow token.

### Dependencies / Related

_No response_

### Additional Context

_No response_

Start at the severity-to-priority GraphQL call and compare its authentication path for AbsaOSS-to-AbsaOSS versus enterprise repositories. Reproduce the SAML enforcement failure with an enterprise repository, then verify either enterprise support or a standalone Python/shell mapping script accepting --token and --api-url. Done means the root cause and workaround or fix are documented in the repository.

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