Init dag dir

[HtcOrange]

As this issue: #530

During the testing process, I found that the scheduler tried to find the directory "$HOME/. dagu/dags" when starting, but it did not create this directory. This can lead to a problem: the scheduler will not be able to start the watcher service when it cannot find this directory, but it will not exit itself. Therefore, when adding a cron task on the page, these cron tasks will not be scheduled. When users perform queries or add tasks on the page, the directory of dags will be automatically created. However, since it is not a hot load, the scheduler will not re read this directory, and subsequent watcher services will never start unless the scheduler is manually killed and restarted.
In summary, I believe that adding an initialization process can effectively solve this problem.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.83%. Comparing base (cc1b134) to head (0fd6976).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #537      +/-   ##
==========================================
+ Coverage   72.75%   72.83%   +0.08%     
==========================================
  Files          43       43              
  Lines        3736     3736              
==========================================
+ Hits         2718     2721       +3     
+ Misses        878      876       -2     
+ Partials      140      139       -1     

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[yohamta]

@HtcOrange Amazing. Thank you so much for fixing the problem 👍