Sensitive estimate data now restricted to authorized roles

Field technicians can no longer view estimate details, pricing, or line items they aren't authorized to access.

Security

Estimate data is now properly restricted by role. Previously, field technicians could view AI-generated line items, unit prices, totals, overhead/profit margins, and tax rates on every phase — despite their role having no estimate permissions.

Estimate data is now hidden across all UI surfaces: the sidebar no longer shows the Estimates link, estimate tabs don't appear on phase details, and direct navigation to estimate URLs safely redirects to the scope view. Server-side validation ensures API calls are also blocked for unauthorized roles.

This closes a confidentiality gap while maintaining full functionality for owner, admin, project manager, and accounting roles.