feat : add my-tasks page with Kanban and List views

Add a /my-tasks page displaying all non-archived tasks across projects
with server-side filtering (assignee, project, group, priority, effort,
tags, status) and two view modes (Kanban columns by status, List view).
Includes sidebar navigation link and i18n translations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/i18n/locales/fr.json

@@ -85,5 +85,21 @@
         "statusFinal": "Statut final",
         "groupArchiveDisabled": "Tous les tickets doivent être en statut final pour archiver le groupe.",
         "groupNonFinalTasks": "Il reste {count} ticket(s) sans statut final dans ce groupe."
+    },
+    "myTasks": {
+        "title": "Mes tâches",
+        "viewKanban": "Vue Kanban",
+        "viewList": "Vue Liste",
+        "allProjects": "Tous les projets",
+        "allGroups": "Tous les groupes",
+        "allTypes": "Tous les types",
+        "allPriorities": "Toutes les priorités",
+        "allEfforts": "Tous les efforts",
+        "allAssignees": "Tous",
+        "noTasks": "Aucune tâche",
+        "backlog": "Backlog"
+    },
+    "sidebar": {
+        "myTasks": "Mes tâches"
     }
 }