feat: add pinned tag functionality and UI enhancements

- Introduced `isPinned` property to the `Tag` model for marking main objectives.
- Updated `TagForm` to include a checkbox for setting tags as pinned, enhancing user interaction.
- Enhanced `KanbanBoardContainer` to display pinned tasks in a dedicated `ObjectivesBoard`, improving task visibility.
- Modified `KanbanFilters` to support filtering by pinned tags, streamlining task management.
- Adjusted `TasksContext` to separate pinned tasks from regular tasks for better organization.

components/forms/TagForm.tsx

@@ -33,7 +33,8 @@ const PRESET_COLORS = [
 export function TagForm({ isOpen, onClose, onSubmit, tag, loading = false }: TagFormProps) {
   const [formData, setFormData] = useState({
     name: '',
-    color: '#3B82F6'
+    color: '#3B82F6',
+    isPinned: false
   });
   const [errors, setErrors] = useState<string[]>([]);
 
@@ -42,12 +43,14 @@ export function TagForm({ isOpen, onClose, onSubmit, tag, loading = false }: Tag
     if (tag) {
       setFormData({
         name: tag.name,
-        color: tag.color
+        color: tag.color,
+        isPinned: tag.isPinned || false
       });
     } else {
       setFormData({
         name: '',
-        color: TagsClient.generateRandomColor()
+        color: TagsClient.generateRandomColor(),
+        isPinned: false
       });
     }
     setErrors([]);
@@ -166,6 +169,30 @@ export function TagForm({ isOpen, onClose, onSubmit, tag, loading = false }: Tag
           </div>
         </div>
 
+        {/* Objectif principal */}
+        <div className="space-y-2">
+          <label className="block text-sm font-mono font-medium text-slate-300 uppercase tracking-wider">
+            Type de tag
+          </label>
+          <div className="flex items-center gap-3">
+            <label className="flex items-center gap-2 cursor-pointer">
+              <input
+                type="checkbox"
+                checked={formData.isPinned}
+                onChange={(e) => setFormData(prev => ({ ...prev, isPinned: e.target.checked }))}
+                disabled={loading}
+                className="w-4 h-4 rounded border border-slate-600 bg-slate-800 text-purple-600 focus:ring-purple-500 focus:ring-2 disabled:cursor-not-allowed"
+              />
+              <span className="text-sm text-slate-300">
+                🎯 Objectif principal
+              </span>
+            </label>
+          </div>
+          <p className="text-xs text-slate-400">
+            Les tâches avec ce tag apparaîtront dans la section "Objectifs Principaux" au-dessus du Kanban
+          </p>
+        </div>
+
         {/* Erreurs */}
         {errors.length > 0 && (
           <div className="bg-red-900/20 border border-red-500/30 rounded-lg p-3">