Fix project/milestone association and redesign AppHeader navigation

Backend:
- routes/tasks.py: POST + PUT were silently dropping project_id,
  milestone_id, parent_id from request body — root cause of association
  not saving from the task editor
- routes/tasks.py: GET /api/tasks/:id now includes parent_title in
  response (secondary lookup when parent_id is set)
- routes/notes.py: add PATCH /api/notes/:id for partial updates (used
  by sub-task status toggle; PUT already existed but PATCH was missing)
- routes/projects.py: GET /api/projects/:id/notes now fetches milestone
  IDs and passes them via milestone_ids so tasks assigned to a milestone
  (but lacking project_id) are included in the project view
- services/notes.py: create_note() auto-sets project_id from milestone
  when milestone_id is provided and project_id is omitted; list_notes()
  gains milestone_ids param — when combined with project_id uses OR
  condition (project_id=X OR milestone_id IN (...))

Frontend:
- NoteEditorView: add MilestoneSelector; milestone resets when project
  changes; all save paths (save/create/auto-save) include milestone_id
- stores/notes.ts: add milestone_id to createNote + updateNote types
- TaskEditorView: sub-tasks now inherit milestone_id from parent task
- AppHeader: three-zone layout — brand left, Notes/Projects/Tasks/Chat
  centered (absolute positioning), right rail with status/theme/? and
  gear dropdown containing Settings/Users/Logs; mobile dropdown unchanged

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

src/fabledassistant/routes/tasks.py

@@ -81,6 +81,9 @@ async def create_task_route():
         priority=priority,
         due_date=due_date,
         tags=tags,
+        project_id=data.get("project_id"),
+        milestone_id=data.get("milestone_id"),
+        parent_id=data.get("parent_id"),
     )
     return jsonify(task.to_dict()), 201
 
@@ -92,7 +95,11 @@ async def get_task_route(task_id: int):
     task = await get_note(uid, task_id)
     if task is None:
         return jsonify({"error": "Task not found"}), 404
-    return jsonify(task.to_dict())
+    data = task.to_dict()
+    if task.parent_id:
+        parent = await get_note(uid, task.parent_id)
+        data["parent_title"] = parent.title if parent else None
+    return jsonify(data)
 
 
 @tasks_bp.route("/<int:task_id>", methods=["PUT"])
@@ -123,6 +130,10 @@ async def update_task_route(task_id: int):
     if "tags" in data:
         fields["tags"] = data["tags"]
 
+    for key in ("project_id", "milestone_id", "parent_id"):
+        if key in data:
+            fields[key] = data[key]
+
     task = await update_note(uid, task_id, **fields)
     if task is None:
         return jsonify({"error": "Task not found"}), 404