docs: update backend database schema section in README

[CodeSparks45]

Before opening: make sure there is an issue tracking this work, and link it below. PRs without a linked issue may be closed without review.

Linked issue

Closes #214

What this PR does

This PR synchronizes the database schema documentation in backend/README.md with the actual SQLite implementation found in backend/app/db.py. It comprehensively documents all six actively initialized tables along with their respective column types, descriptions, and foreign key relationships to eliminate documentation drift.

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

Stack affected

• Backend
• Frontend
• Both

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Changes

Backend

• Replaced the outdated ## Database Schema section in backend/README.md with accurate markdown tables representing the current database state.

Frontend

New dependencies

Database / schema changes

• Documented missing tables (org_jobs, verify_outcomes, contributor_stats, dependency_links).
• Documented newly appended columns in existing tables (e.g., package_name, ml_score, false_positive in findings).

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Testing

How did you test this?

Performed a manual cross-reference between the SQL CREATE TABLE and ALTER TABLE execution queries in backend/app/db.py and the newly formatted markdown tables. Rendered the markdown locally in VS Code to ensure standard GitHub Flavored Markdown (GFM) table formatting is visually intact and readable.

Checklist

• Tested locally end-to-end (upload ZIP or GitHub URL → scan → findings returned correctly)
• New ML model falls back gracefully when model file is absent
• 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

No complex logic changes. Please verify that the documented columns align exactly with the current db.py initialization logic.

Screenshots (if UI changed)

[github-actions]

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[github-actions]

✅ PR template check passed!

@arpit2006 this PR is ready for your review. 🚀

[arpit2006]

@CodeSparks45 !
Create a docs folder and create this database.md in there and link it on readme to ensure good experience.

[arpit2006]

Create folder and add it there

[arpit2006]

@CodeSparks45