Update README with Complete Setup and Backend Overview

[rathorvikash010-netizen]

Summary

This pull request significantly improves the project README to make onboarding, development, and understanding the CoRE Stack Backend easier for new contributors and users.

Key Changes

• Added a clear project overview describing the purpose and scope of the CoRE Stack backend.
• Introduced a step-by-step installation guide using the provided Linux installation script, including prerequisites and runtime instructions.
• Documented server execution steps, including Django and Celery worker setup.
• Added a detailed project structure section, explaining all major Django applications and their responsibilities.
• Included a comprehensive technology stack overview covering Django, PostgreSQL/PostGIS, Celery, Apache, and GEE.
• Added a script path reference table mapping domain themes to computation pipelines.
• Documented all required environment variables, grouped by service (Database, Django, ODK, GeoServer, GEE, AWS, etc.).
• Added commonly used development commands for migrations, static files, superuser creation, and testing.
• Expanded API documentation references, including Swagger, ReDoc, and versioned API endpoints.
• Included links to integration guides, database design references, and external API documentation.

Purpose

The goal of this update is to:

• Reduce setup friction for new contributors
• Provide a single, authoritative reference for backend configuration
• Improve maintainability and clarity of the repository documentation

Notes

• No functional or code changes are introduced in this PR.
• Changes are documentation-only and backward compatible.

Please let me know if you’d like the README split into multiple documents or further refined.

[rathorvikash010-netizen]

Hii @ankit-work7 @amanodt @kapildadheech

This PR improves the README with complete setup instructions, project structure, and API documentation.

Kindly review and let me know if any changes are required.
Thanks!