chore: release v0.13.0 - merge develop to master

[Copilot]

Merges develop branch to master for 0.13.0 release.

⚠ Breaking Changes

Environment variable names renamed to avoid conflicts with system-wide env vars:

• USERNAME → HEXON_USERNAME
• PASSWORD → HEXON_PASSWORD

Changes

• Environment config: Updated .env.sample and server-shared/src/env-service.ts with prefixed variable names
• Version bump: 0.12.8 → 0.13.0
• Changelog: Added 0.13.0 release notes
• Documentation: Updated README to reference develop branch for contributions
• Build artifacts: Rebuilt server with updated env handling

// Before
const username = process.env.USERNAME
const password = process.env.PASSWORD

// After  
const username = process.env.HEXON_USERNAME
const password = process.env.HEXON_PASSWORD

Original prompt

merge devlop to master and build release 0.13.0

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