refactor(skills): compress specialist skill contracts

[Alan-TheGentleman]

Context

This is PR 4 of a chained feature-branch refactor to standardize repository skills around a clearer runtime format.

This batch compresses the largest specialist skills while preserving the critical operational rules that matter for implementation and review.

Description

• Refactors the largest specialist skills into compact runtime contracts
• Preserves the highest-risk operational rules for compliance, Django/Postgres migrations, PostgreSQL indexing, and Attack Paths query authoring
• Replaces handbook-scale inline prose with local references and explicit output expectations

Chain Context

• Strategy: feature-branch-chain
• Tracker branch: feat/skill-style-guide-refactor
• Depends on: refactor(skills): compact core Prowler contracts #11089
• Current PR: 4 / 4 📍
• Base branch: refactor/skill-style-core-prowler
• This is the final child PR in the current chain

feat/skill-style-guide-refactor
└── refactor/skill-style-meta-foundation
    └── refactor/skill-style-core-generic
        └── refactor/skill-style-core-prowler
            └── refactor/skill-style-specialists 📍

Steps to review

1. Review the four specialist skills:
   • skills/prowler-compliance/SKILL.md
   • skills/django-migration-psql/SKILL.md
   • skills/postgresql-indexing/SKILL.md
   • skills/prowler-attack-paths-query/SKILL.md
2. Confirm each file now follows the same contract shape with trigger-first frontmatter and explicit output contract
3. Spot-check that the critical invariants were preserved:
   • compliance layer and formatter rules
   • safe migration and backfill constraints
   • indexing validation and maintenance rules
   • Attack Paths scoping and isolation rules
4. Confirm the batch contains only the specialist skills and no spillover into other parts of the repo

Validation performed:

• Structural RED/GREEN validation for trigger-first descriptions, required section order, and local-only references
• skill-sync intentionally skipped because no metadata-driven surfaces changed

Checklist

Community Checklist

• This feature/issue is listed in here or roadmap.prowler.com
• Is it assigned to me, if not, request it via the issue/feature in here or Prowler Community Slack

• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.
• Review if is needed to change the Readme.md
• Ensure new entries are added to CHANGELOG.md, if applicable.

SDK/CLI

• Are there new checks included in this PR? No
  • If so, do we need to update permissions for the provider? Please review this carefully.

UI

• All issue/task requirements work as expected on the UI
• Screenshots/Video of the functionality flow (if applicable) - Mobile (X < 640px)
• Screenshots/Video of the functionality flow (if applicable) - Table (640px > X < 1024px)
• Screenshots/Video of the functionality flow (if applicable) - Desktop (X > 1024px)
• Ensure new entries are added to CHANGELOG.md, if applicable.

API

• All issue/task requirements work as expected on the API
• Endpoint response output (if applicable)
• EXPLAIN ANALYZE output for new/modified queries or indexes (if applicable)
• Performance test results (if applicable)
• Any other relevant evidence of the implementation (if applicable)
• Verify if API specs need to be regenerated.
• Check if version updates are required (e.g., specs, Poetry, etc.).
• Ensure new entries are added to CHANGELOG.md, if applicable.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.