Add validation for required environment variables on startup

[djdiptayan1]

Description:
The application starts successfully even when critical environment variables are missing, leading to runtime errors.

Current Issues:

• No validation of required environment variables
• Application starts with missing config
• Runtime errors due to undefined variables
• No clear error messages for config issues
• Default values not properly set

What needs to be fixed:

• Add startup validation for required env vars
• Provide clear error messages for missing config
• Set appropriate default values where possible
• Create environment variable documentation
• Add configuration validation middleware

Acceptance Criteria:

• Application fails fast on missing required env vars
• Clear error messages indicate which vars are missing
• Default values are documented and applied
• Configuration validation runs on startup
• Environment-specific configs are validated

Files to modify:

• index.js
• Create src/config/validation.js

[saura8668]

Hi @djdiptayan1 can you assign me this issue?

[rishu-7549]

Hey @djdiptayan1, could you please assign this issue to me? I'd love to work on it!
Also, just wanted to confirm, is this project accepted for Hacktoberfest 2025? Just making sure before I start. 😊

[sebyx07]

Just submitted PR with comprehensive environment variable validation. The new system validates all required variables on startup, provides clear error messages, applies smart defaults, and prevents runtime configuration errors.