Add Spec Kit docs and improve CONTRIBUTING.md

Summary

This issue tracks the addition of Spec Kit documentation and an improved CONTRIBUTING.md for the Civic Scam Shield project.

Changes

New files (Spec Kit workflow):

• specs/001-civic-scam-shield/spec.md — User stories & requirements (WHAT & WHY)
• specs/001-civic-scam-shield/plan.md — Tech stack, architecture, component breakdown
• specs/001-civic-scam-shield/tasks.md — 35 ordered implementation tasks across 5 phases

Updated files:

• Pratham_AI_Docs/CONTRIBUTING.md — Restructured with project tree, code blocks, and step-by-step guides for adding languages and file types

Branch

All changes pushed to backend branch, then merged into main.