feat(time-tracking) : extract time-tracking front into Nuxt module layer

Companion to the backend module migration (LST-64). The Nuxt layer is
auto-detected from frontend/modules/* — no nuxt.config change needed.

- Move page, timer store, time-entries service + DTO and the 6 time-tracking
  components into frontend/modules/time-tracking/.
- Rewrite explicit service/DTO imports to ~/modules/time-tracking/* (store and
  components stay auto-imported); update the dashboard (index.vue) consumer.
- Route /time-tracking preserved; i18n keys kept in the global locale file.

nuxt build passes; /time-tracking routed.

frontend/modules/time-tracking/services/dto/time-entry.ts

@@ -0,0 +1,28 @@
+import type { UserData } from '~/services/dto/user-data'
+import type { Project } from '~/services/dto/project'
+import type { Task } from '~/services/dto/task'
+import type { TaskTag } from '~/services/dto/task-tag'
+
+export type TimeEntry = {
+    id: number
+    '@id'?: string
+    title: string | null
+    description: string | null
+    startedAt: string
+    stoppedAt: string | null
+    user: UserData
+    project: Project | null
+    task: Task | null
+    tags: TaskTag[]
+}
+
+export type TimeEntryWrite = {
+    title?: string | null
+    description?: string | null
+    startedAt: string
+    stoppedAt?: string | null
+    user: string
+    project?: string | null
+    task?: string | null
+    tags?: string[]
+}