feat: add optional .env support for environment configuration

[maishivamhoo123]

Summary

This PR adds optional support for loading environment variables from a .env file to improve local development experience.

Changes

• Load .env file at startup if it exists (ignored if missing)
• Add .env.example with empty default values
• Add .env to .gitignore

Backward Compatibility

• No behavior change if .env is not present
• Existing OS environment variables continue to work
• Production and container-based deployments are unaffected

Related Issue

Closes #1450

[LinkinStars]

@maishivamhoo123 You submitted language and configuration files that should not have been submitted.

[maishivamhoo123]

Sorry sir for the confusion. I won’t repeat this again.
Just to confirm, I should add only the following files:

main.go

.env.example

.gitignore

README.md

go.mod
@LinkinStars Sir Please let me know if this is correct.
Thank you for your guidance, sir.

[LinkinStars]

Sorry sir for the confusion. I won’t repeat this again. Just to confirm, I should add only the following files:

main.go

.env.example

.gitignore

README.md

go.mod @LinkinStars Sir Please let me know if this is correct. Thank you for your guidance, sir.

@maishivamhoo123 I think we can skip modifying README.md. We can add this instructions to https://answer.apache.org/docs/env

[maishivamhoo123]

Understood, @LinkinStars sir.
So instead of modifying README.md, I should add the relevant instructions to the documentation at https://answer.apache.org/docs/env
.
Thank you for your guidance.

[maishivamhoo123]

@LinkinStars Sir,
I hope this PR looks good now. If there are any remaining issues or further improvements needed, please let me know—I’ll be happy to address them.

Thank you for your guidance .