GitHub Environments & Secrets #72

Priority: High
Difficulty: Medium

Description:
Set up GitHub Environments for dev and prod, and configure environment-specific secrets.

• Add secrets: MONGODB_URI_DEV, MONGODB_URI_PROD (placeholder), and GRAFANA_CLOUD_API_KEY (placeholder).
• Ensure secrets are only accessible in their respective environment workflows.
• Enable required reviewers for the prod environment.

Acceptance Criteria:

• dev and prod environments are created in GitHub
• Environment secrets are set and scoped correctly
• Secrets are only accessible in the corresponding environment workflows
• Required reviewers are enabled for the prod environment