feat(notifications): implement high-risk finding alerting workflows and configuration UI

[YerraguntaAjayKumar]

Description

This PR implements production-grade notification channels for high-risk and critical findings inside SecuScan as requested in #254.

Key Contributions:

• Database Engine (backend/secuscan/database.py, models.py): Added SQLite schema migrations for notification_rules and notification_history tracking along with structured Pydantic schemas.
• Service Layer (backend/secuscan/notifications.py, executor.py): Built an isolated background notification service. Implemented a 1-hour duplicate cooldown window for deduplication, payload routing (Webhook/Email placeholders), and strict metadata data redaction to isolate raw tokens or internal code snippets.
• Frontend Panel (frontend/src/components/NotificationSettings.tsx, pages/Settings.tsx): Created a clean, responsive neo-brutalist alerting configuration interface tied directly into a centralized api.ts request pattern to eliminate lockfile or formatting churn.

Related Issues

Closes #254

Type of Change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Implemented a comprehensive unit test suite inside testing/backend/unit/test_notifications.py ensuring successful route verification, failed network handling delivery states, data redaction assertions, and 3600-second token deduplication logic.

Checklist

• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.

[utksh1]

Closing this one as invalid for now. The notification feature is extremely large and not reviewable in its current shape; the new notifications.py file contains massive whitespace/churn, formatting-hygiene is failing, and the implementation needs to be split into smaller backend/API/frontend/test PRs before it can be safely reviewed. Marked gssoc:invalid and gssoc:ai-slop because the submitted code quality is not acceptable for merge.

[Pragati5-DEBUG]

Hi @utksh1,

I saw #360 was closed. I want to help on #254, but in small PRs.

Can I start with only database tables + models first (no UI, no alerts yet)?

Thanks!