feat: add SQLite schema and db.py for scan findings

[khushboo-khatoon]

Closes #1

What this PR does

Adds persistent SQLite storage for scan findings. Creates backend/app/db.py with init_db() and get_db() functions, initializes the database on server startup, and documents the schema in backend/README.md.

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

Changes

Backend

• Added backend/app/db.py with init_db() and get_db() using aiosqlite
• Added @app.on_event("startup") in main.py to call init_db() on boot
• Added backend/README.md with full schema documentation

New dependencies

• aiosqlite — async SQLite driver for non-blocking DB access in FastAPI

Database / schema changes

• New table: findings (id, job_id, rule_id, severity, category, file_path, line_number, cwe, scanner, message, created_at)
• New table: jobs (job_id, project_name, scan_method, created_at)
• patchpilot.db auto-created in backend/ on first server boot

Testing

Started server locally — patchpilot.db was created automatically in backend/ on first boot.

Checklist

• Tested locally end-to-end
• No new console.error or unhandled Python exceptions introduced
• requirements.txt updated with aiosqlite

Anything reviewers should focus on

db.py implementation — especially get_db() and init_db() functions.

[khushboo-khatoon]

Hey @ionfwsrijan,

u can review and merge the PR , if all are okay

Thank you for all your help throughout the process (:

[Copilot]

Pull request overview

This PR introduces persistent SQLite storage for scan findings in the FastAPI backend by adding a database module, initializing schema creation on server startup, and documenting the schema.

Changes:

• Added backend/app/db.py with SQLite schema initialization (init_db) and a database connection helper (get_db) using aiosqlite.
• Initialized the database on API startup via a FastAPI startup hook in backend/app/main.py.
• Documented the jobs and findings tables in backend/README.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 9 comments.

File	Description
backend/app/db.py	Adds SQLite path, schema initialization, and DB connection helper.
backend/app/main.py	Calls init_db() on application startup.
backend/README.md	Documents the SQLite schema and where the DB file is created.

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[ionfwsrijan]

@khushboo-khatoon Failing checks

[ionfwsrijan]

@khushboo-khatoon LGTM. Great work. Merging this now.