fix: load tasks via TasksApi in Knowledge view, remove tab counts

Tasks are not part of the knowledge API (backend rejects type=task).
When the Tasks tab is selected, fetch from /api/tasks and convert to
KnowledgeItem. Also removes per-type counts from tab labels to prevent
tabs from awkwardly resizing when counts load.

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

lib/data/models/knowledge_item.dart

@@ -1,3 +1,5 @@
+import 'task.dart';
+
 class KnowledgeItem {
   final int id;
   final String noteType; // 'note' | 'person' | 'place' | 'list' | 'task'
@@ -30,6 +32,22 @@ class KnowledgeItem {
     required this.updatedAt,
   });
 
+  factory KnowledgeItem.fromTask(Task task) => KnowledgeItem(
+        id: task.id,
+        noteType: 'task',
+        title: task.title,
+        body: task.description ?? '',
+        tags: const [],
+        projectId: task.projectId,
+        milestoneId: task.milestoneId,
+        parentId: task.parentId,
+        status: task.status.value,
+        priority: task.priority.value,
+        dueDate: task.dueDate?.toIso8601String(),
+        createdAt: task.createdAt,
+        updatedAt: task.updatedAt,
+      );
+
   factory KnowledgeItem.fromJson(Map<String, dynamic> json) => KnowledgeItem(
         id: json['id'] as int,
         noteType: json['note_type'] as String? ?? 'note',