feat(5.21): Tasks Plugin — activities with status, priority, due dates, ARQ reminders

- New builtin plugin app/plugins/builtins/tasks/ with full CRUD
- Task model with TenantMixin (title, description, status, priority, due_date, assigned_to, contact_id)
- Routes: GET/POST /tasks, GET/PATCH/DELETE /tasks/{id}, POST /tasks/{id}/assign, POST /tasks/{id}/status
- All routes RBAC-protected (tasks:read, tasks:write, tasks:delete)
- ARQ cron job tasks_due_reminder (daily 8:00) sends notifications for due tasks
- Migration 0001_initial.sql creates tasks table with indexes
- Frontend: Tasks.tsx page with list, filter, create/edit modal, detail modal
- Frontend: api/tasks.ts with React Query hooks
- Route /tasks in routes/index.tsx, sidebar entry via plugin manifest
- i18n keys for nav.tasks and tasks.* in de.json and en.json
- Tests: test_tasks.py (11 tests) + Tasks.test.tsx (3 tests)
- Registered TasksPlugin in conftest.py and worker.py

frontend/src/i18n/locales/de.json

@@ -18,7 +18,8 @@
     "settings": "Einstellungen",
     "aiAssistant": "KI Assistent",
     "mcpSettings": "MCP Einstellungen",
-    "reports": "Reports"
+    "reports": "Reports",
+    "tasks": "Aufgaben"
   },
   "auth": {
     "login": "Anmelden",
@@ -996,5 +997,30 @@
     "selectTemplateHint": "Wählen Sie eine Vorlage aus der Liste",
     "downloadHistory": "Download-Verlauf",
     "noDownloads": "Noch keine Downloads"
+  },
+  "tasks": {
+    "title": "Aufgaben",
+    "create": "Neue Aufgabe",
+    "edit": "Aufgabe bearbeiten",
+    "deleteConfirm": "Diese Aufgabe löschen?",
+    "created": "Aufgabe erstellt",
+    "updated": "Aufgabe aktualisiert",
+    "deleted": "Aufgabe gelöscht",
+    "statusUpdated": "Status aktualisiert",
+    "noTasks": "Keine Aufgaben",
+    "noTasksDesc": "Es wurden noch keine Aufgaben erstellt.",
+    "markDone": "Erledigt",
+    "dueDate": "Fälligkeitsdatum",
+    "title_field": "Titel",
+    "description": "Beschreibung",
+    "status_field": "Status",
+    "priority_field": "Priorität",
+    "statusOpen": "Offen",
+    "statusInProgress": "In Bearbeitung",
+    "statusDone": "Erledigt",
+    "priorityLow": "Niedrig",
+    "priorityMedium": "Mittel",
+    "priorityHigh": "Hoch",
+    "priorityUrgent": "Dringend"
   }
 }

frontend/src/i18n/locales/en.json

@@ -18,7 +18,8 @@
     "settings": "Settings",
     "aiAssistant": "AI Assistant",
     "mcpSettings": "MCP Settings",
-    "reports": "Reports"
+    "reports": "Reports",
+    "tasks": "Tasks"
   },
   "auth": {
     "login": "Sign In",
@@ -996,5 +997,30 @@
     "selectTemplateHint": "Select a template from the list",
     "downloadHistory": "Download History",
     "noDownloads": "No downloads yet"
+  },
+  "tasks": {
+    "title": "Tasks",
+    "create": "New Task",
+    "edit": "Edit Task",
+    "deleteConfirm": "Delete this task?",
+    "created": "Task created",
+    "updated": "Task updated",
+    "deleted": "Task deleted",
+    "statusUpdated": "Status updated",
+    "noTasks": "No tasks",
+    "noTasksDesc": "No tasks have been created yet.",
+    "markDone": "Mark Done",
+    "dueDate": "Due Date",
+    "title_field": "Title",
+    "description": "Description",
+    "status_field": "Status",
+    "priority_field": "Priority",
+    "statusOpen": "Open",
+    "statusInProgress": "In Progress",
+    "statusDone": "Done",
+    "priorityLow": "Low",
+    "priorityMedium": "Medium",
+    "priorityHigh": "High",
+    "priorityUrgent": "Urgent"
   }
 }