Implement post-fix rescan and finding diffing for verify outcomes

[sasidaran-99]

Linked issue

Closes #27

What this PR does

Implements post-fix rescanning and finding diffing for verify outcomes. The /verify endpoint now re-runs security scanners, compares the results against the baseline findings stored during the initial scan, calculates newly introduced findings, and updates the verification outcome accordingly.

Type of change

• Bug fix
• New feature
• ML model / training pipeline
• Refactor (no behaviour change)
• Documentation
• Tests only

ML tier (if applicable)

• Tier 1 — Triage
• Tier 2 — Predictive
• Tier 3 — Autonomous
• Not ML-related

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Changes

Backend

• Added baseline finding retrieval from the database.
• Re-ran scanners during /verify.
• Implemented finding diffing using rule_id, file_path, and line_number.
• Calculated actual new_issues_introduced values.
• Updated passed status to require both successful verification and zero newly introduced findings.
• Added logging for verification outcomes.

Database / schema changes

• No schema changes required.

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Testing

How did you test this?

• Tested locally using the FastAPI Swagger UI.
• Uploaded a sample ZIP project using /scan.
• Verified findings were stored and a valid job_id was generated.
• Executed /verify using the generated job_id.
• Confirmed verification outcomes were persisted correctly and the endpoint returned expected results.
• Ran Ruff checks and formatting successfully.

Checklist

• Tested locally end-to-end (upload ZIP or GitHub URL → scan → findings returned correctly)
• No new console.error or unhandled Python exceptions introduced
• Added or updated tests where applicable
• requirements.txt / package.json updated if new dependencies added
• New model files (.pkl, .pt, etc.) are gitignored, not committed

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Anything reviewers should focus on

Please review the finding comparison logic used to identify newly introduced findings and the updated verification outcome calculation.

[sasidaran-99]

@ionfwsrijan,
Done with the issue. Kindly do check it and merge it.

[ionfwsrijan]

@sasidaran-99 LGTM merging it