fix(UX): Item master form cleanup (backport #54538)

[mergify]

Issues with current form:

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• All field need tooltip for better understanding of the purpose.

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• Checkboxes need description/tooltip

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After the refactor:

Screen.Recording.2026-04-28.at.5.25.19.PM.mov

More UX issue:

• Saving an item with opening stock silently creates a stock entry without notifying the user.

Screen.Recording.2026-04-28.at.5.39.23.PM.mov

• Saving an item with a Standard Selling Rate creates an Item Price record without any user notification.

Screen.Recording.2026-04-28.at.5.32.48.PM.mov

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This is an automatic backport of pull request #54538 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.76%. Comparing base (64a724b) to head (0eb049c).
⚠️ Report is 46 commits behind head on version-16-hotfix.

Files with missing lines	Patch %	Lines
erpnext/stock/doctype/item/item.py	75.00%	3 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           version-16-hotfix   #54634      +/-   ##
=====================================================
+ Coverage              79.46%   79.76%   +0.29%     
=====================================================
  Files                   1172     1172              
  Lines                 126286   126456     +170     
=====================================================
+ Hits                  100354   100862     +508     
+ Misses                 25932    25594     -338     

Files with missing lines	Coverage Δ
...port/bom_stock_analysis/test_bom_stock_analysis.py	100.00% <ø> (ø)
erpnext/stock/doctype/item/item.py	84.22% <75.00%> (-0.21%)	⬇️

... and 5 files with indirect coverage changes

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