[BE] CSP policy propagation loading indicators and progress tracking

Problem

When admins designate/update CSP groups or update CSP policies, propagation happens asynchronously with no visual feedback. Users don't know when CSP changes are being applied or when they're complete.

Solution

Extend foundation policy progress tracking (#528300 (closed)) for CSP-specific scenarios with optimizations for large-scale propagations.

Requirements (MoSCoW)

Must Have:

• CSP propagation indicator in Admin Settings (instance-wide)
• Propagation indicator in affected group/project Policy pages
• Distinguish CSP designation changes vs CSP policy updates
• Performance optimization for large-scale CSP propagations

Should Have:

• CSP progress percentage with scope info
• CSP group name and affected target count
• Context-appropriate detail (Admin vs group/project views)

Could Have:

• Detailed CSP propagation information per target
• CSP propagation history
• Granular failure tracking

Would Have:

• Time estimation for CSP propagations
• CSP analytics and historical data
• Advanced retry mechanisms

UI Locations

Admin Settings:

• Must: "CSP policies are being propagated"
• Should: "Propagating policies from CSP group 'security': 60% complete"

Group/Project Policy Pages:

• Must: "Policies are being updated from CSP"
• Should: Progress specific to that target

Dependencies

• Requires foundation infrastructure from #528300 (closed) Phase 1