feat(tasks): complete task management system with Kanban, Calendar, notifications

- Add Task model with subtasks, priorities, status transitions, dates, hours
- Add Comment polymorphic model for tasks/issues/projects
- Livewire components: TaskManager (list+filters), TaskForm (modal), TaskDetail, TaskKanban (drag&drop), TaskCalendar (FullCalendar)
- TaskPolicy with permissions (view/create/edit/delete/assign/manage all)
- Notifications: assigned, status change, overdue, comment added
- Daily overdue notification job scheduled
- Dashboard widget unifies IssueTask + Task
- i18n: en/es/fr/ru (393 keys each)
- Routes, navigation, offline sync support
- 101 tests passing, Pint compliant on new files

public/images/flags/fr.svg

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 750 500">
+  <rect width="250" height="500" fill="#002654"/>
+  <rect x="250" width="250" height="500" fill="#FFFFFF"/>
+  <rect x="500" width="250" height="500" fill="#ED2939"/>
+</svg>

public/images/flags/ru.svg

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 750 500">
+  <rect width="750" height="166.67" fill="#FFFFFF"/>
+  <rect y="166.67" width="750" height="166.66" fill="#0039A6"/>
+  <rect y="333.33" width="750" height="166.67" fill="#D52B1E"/>
+</svg>