refactor(i18n) : replace hardcoded French strings with i18n keys

Replace 30+ hardcoded strings across 15 components with $t() calls.
Added keys for common actions, drawers titles, empty states, and modals.

Ticket: T-020

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/components/time-tracking/TimeEntryDrawer.vue

@@ -1,5 +1,5 @@
 <template>
-    <AppDrawer v-model="isOpen" :title="isEditing ? 'Modifier un temps' : 'Ajouter une Activité'">
+    <AppDrawer v-model="isOpen" :title="isEditing ? $t('timeEntries.editEntry') : $t('timeEntries.addEntry')">
         <form class="space-y-4" @submit.prevent="onSubmit">
             <div>
                 <label class="mb-1 block text-sm font-semibold text-neutral-700">Titre</label>
@@ -117,7 +117,7 @@
 </template>
 
 <script setup lang="ts">
-import type { TimeEntry } from '~/services/dto/time-entry'
+import type { TimeEntry, TimeEntryWrite } from '~/services/dto/time-entry'
 import type { UserData } from '~/services/dto/user-data'
 import type { Project } from '~/services/dto/project'
 import type { TaskTag } from '~/services/dto/task-tag'
@@ -257,7 +257,7 @@ async function onSubmit() {
     if (isEditing.value && props.entry) {
         await update(props.entry.id, payload)
     } else {
-        await create(payload as any)
+        await create(payload as TimeEntryWrite)
     }
 
     emit('saved')