Database: time_entries, billing_rates, invoices tables with RLS.
Backend: CRUD services+handlers for time entries, billing rates, invoices.
- Time entries: list/create/update/delete, summary by case/user/month
- Billing rates: upsert with auto-close previous, current rate lookup
- Invoices: create with auto-number (RE-YYYY-NNN), status transitions
(draft->sent->paid, cancellation), link time entries on invoice create
API: 11 new endpoints under /api/time-entries, /api/billing-rates, /api/invoices
Frontend: Zeiterfassung tab on case detail, /abrechnung overview with filters,
/abrechnung/rechnungen list+detail with status actions, billing rates settings
Also: resolved merge conflicts between audit-trail and role-based branches,
added missing types (Notification, AuditLogResponse, NotificationPreferences)
