[FRONTEND] Add report diff view with finding-level changes

[utksh1]

Problem

SecuScan needs a production-grade improvement in this area: Comparing security posture over time..

Scope

Let users compare two reports and highlight new, fixed, unchanged, and severity-changed findings.

Acceptance Criteria

• The implementation is focused and does not introduce unrelated UI, docs, lockfile, or formatting churn.
• Security-sensitive behavior has explicit negative tests where applicable.
• Existing tests continue to pass, and new tests cover the main success and failure paths.
• Documentation or configuration examples are updated when operator behavior changes.

Verification

Tests should cover matching logic, severity changes, empty reports, and large diff rendering.

Difficulty

Hard, useful issue intended for experienced contributors.

[Shikhar-404exe]

Hi ,

I reviewed this issue and the related files. I have experience in this field of work.

I’d like to work on this issue and can start immediately. My plan is to:

reproduce the issue locally
trace the affected components
implement and test the fix carefully

Please add suitable labels and /assign this issue to me under gssoc26 if it's available.
Thank you!

[YerraguntaAjayKumar]

Hi @utksh1, I am a GSSoC '26 contributor and would love to take on this issue to implement the report diff view component!

Here is my target implementation plan:

1. Diff Logic & Performance: Build a clean, optimized helper utility to compare two JSON report objects, identifying new, fixed, unchanged, and severity-escalated findings based on unique vulnerability IDs/hashes. I'll ensure it handles large datasets efficiently to prevent main-thread UI lag.
2. UI & UX: Render a scannable, side-by-side or unified diff container in React utilizing status-coded semantic badges (e.g., green for fixed, red for new, orange for severity changes) matching the current UI guidelines.
3. Robust Testing: Write explicit unit tests covering edge cases like entirely empty reports, identical reports, and severe-variant delta shifts.
4. Clean Code: Keep the implementation highly focused to prevent any lockfile, lint, or formatting churn.

If this looks good, please assign this issue to me!