feat: enhance metrics dashboard with new components and data handling

- Introduced `MetricsOverview`, `MetricsMainCharts`, `MetricsDistributionCharts`, `MetricsVelocitySection`, and `MetricsProductivitySection` for improved metrics visualization.
- Updated `MetricsTab` to integrate new components and streamline data presentation.
- Added compatibility fields in `JiraTask` and `AssigneeDistribution` for better data handling.
- Refactored `calculateAssigneeDistribution` to include a count for total issues.
- Enhanced `JiraAnalyticsService` and `JiraAdvancedFiltersService` to support new metrics calculations.
- Cleaned up unused imports and components for a more maintainable codebase.

src/contexts/UserPreferencesContext.tsx

@@ -39,11 +39,38 @@ const UserPreferencesContext = createContext<UserPreferencesContextType | null>(
 
 interface UserPreferencesProviderProps {
   children: ReactNode;
-  initialPreferences: UserPreferences;
+  initialPreferences?: UserPreferences;
 }
 
+const defaultPreferences: UserPreferences = {
+  kanbanFilters: {
+    search: '',
+    tags: [],
+    priorities: [],
+    showCompleted: false,
+    sortBy: 'priority'
+  },
+  viewPreferences: {
+    compactView: false,
+    swimlanesByTags: false,
+    showObjectives: true,
+    showFilters: true,
+    objectivesCollapsed: false,
+    theme: 'light',
+    fontSize: 'medium'
+  },
+  columnVisibility: {
+    hiddenStatuses: []
+  },
+  jiraConfig: {
+    enabled: false
+  },
+  jiraAutoSync: false,
+  jiraSyncInterval: 'daily'
+};
+
 export function UserPreferencesProvider({ children, initialPreferences }: UserPreferencesProviderProps) {
-  const [preferences, setPreferences] = useState<UserPreferences>(initialPreferences);
+  const [preferences, setPreferences] = useState<UserPreferences>(initialPreferences || defaultPreferences);
   const [isPending, startTransition] = useTransition();
 
   // Synchroniser le thème avec le ThemeProvider global (si disponible)