feat(reporting) : add Reporting dashboard front layer

LST-59 (3.1) front. Completes the Reporting module.

- New frontend/modules/reporting/ layer (auto-detected): /reporting page
  (admin middleware) consuming the 4 read-only report endpoints.
- Filters (period presets + custom dates, project, user). 4 sections (time per
  project, time per user, tasks by status, absences by type) each with a
  DataTable + a Chart.js chart (reused global registration).
- Front-side CSV export per section (useCsvExport: BOM UTF-8, ; separator).
- i18n keys (reporting.*, sidebar.admin.reporting).

nuxt build passes; /reporting routed; no route regression.

frontend/modules/reporting/services/dto/reporting.ts

@@ -0,0 +1,34 @@
+export type TimePerProject = {
+    projectId: number
+    projectCode: string
+    projectName: string
+    hours: number
+    entryCount: number
+}
+
+export type TimePerUser = {
+    userId: number
+    username: string
+    fullName: string
+    hours: number
+    entryCount: number
+}
+
+export type TasksByStatus = {
+    statusId: number
+    statusLabel: string
+    count: number
+}
+
+export type AbsencesByType = {
+    type: string
+    count: number
+    totalDays: number
+}
+
+export type ReportFilters = {
+    from: string
+    to: string
+    userId?: number | null
+    projectId?: number | null
+}