[JHC56]

Summary

Fixes #43923

In visual Hourly mode, the next run list skipped a month after midnight on the last day of a month (for example "October 31" right after September 30 11:00 PM). setHours already rolls into the next day, month and year, so the extra overflow block is removed. Added tests for a month end and for New Year.

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've verified the change and added or updated tests where meaningful regression risk justifies coverage.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and vp staged (frontend) to appease the lint gods

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.83%. Comparing base (d562cc0) to head (f908065).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #43925   +/-   ##
=======================================
  Coverage   88.83%   88.83%           
=======================================
  Files        5321     5322    +1     
  Lines      329271   329258   -13     
  Branches    65972    65967    -5     
=======================================
+ Hits       292497   292500    +3     
+ Misses      31552    31536   -16     
  Partials     5222     5222           

Flag	Coverage Δ
dify-ui	91.97% <ø> (+0.05%)	⬆️
web	89.18% <ø> (+<0.01%)	⬆️

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