Milestone 04: Backend Completion

Implemented in this milestone

Added operator queues for assigned reports, open unassigned reports and reports assigned to other operators.
Added an operator intervention summary with report data, citizen contact data, media and latest messages.
Added local in-app notifications for status changes, team assignment, report messages and reward events.
Added citizen reward ledger APIs and automatic points for resolved reports.
Added report/message moderation flags with admin/operator review and optional report rejection.
Expanded admin statistics with category, team, monthly and segmented resolution-time aggregates.
Added anonymized public open-data report export.
Updated the manual OpenAPI contract for the new backend routes.