SPRW-3110: Implement Weekly Digest Email with Dev Testing Controls

[mayankjha-eng]

Description

Implemented weekly digest email for registered users with personalized metrics and activity insights.

• Added weekly digest email with execution trends, key metrics, collaboration updates, and pending actions
• Integrated batch processing to handle users efficiently without overloading the server
• Used precomputed metrics for optimized data fetching and reduced database load
• Implemented controlled email sending with concurrency handling
• Added DEV environment handling to send emails only to QA account for safe testing
• Enabled dynamic date range handling (current week for testing, production-ready for weekly schedule)

This ensures scalable, efficient, and safe email delivery while maintaining accurate user insights.

Add Issue Number

SPRW-3110

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Contribution Checklist:

• The pull request only addresses one issue or adds one feature.
• I have linked an issue to the pull request.
• I have linked a PR type label to the pull request.
• The pull request does not introduce any breaking changes
• I have added screenshots or gifs to help explain the change if applicable.
• I have read the contribution guidelines.

Note: Keeping the PR small and focused helps make it easier to review and merge. If you have multiple changes you want to make, please consider submitting them as separate pull requests.