Add Upcoming Features Plan document outlining new feature proposals for Blazor Data Orchestrator

- Introduced a comprehensive plan detailing features such as Dashboard Analytics, Notifications & Alerts, Agent Monitoring, User & Role Management, Job Dependency Chains, Secrets Management, Bulk Operations, Job Templates Library, Export/Import Jobs, and Audit Log.
- Included priority overview, implementation roadmap, and high-level database schema additions.
- Each feature section contains an overview, requirements, and UI mockups to guide development.

Author: imsaadawais