5004 Show 0 instead of “Unknown” for inactive items in itemized reports

[hagiya0121]

Resolves #5004

Description

In itemized reports, inactive items previously displayed "Unknown" for Total On Hand.
Since items can only be deactivated when their inventory is already 0, the correct value should be 0 instead of "Unknown".
This update removes the "Unknown" fallback in the views and ensures that DistributionItemizedBreakdownService uses a hash with a default value of 0, so inactive items now return 0 instead of nil.
A test has also been added to confirm that inactive items correctly display 0 in reports.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Added a unit test for DistributionItemizedBreakdownService to ensure inactive items' current_onhand is 0.
• Manually verified that inactive items display 0 (not "Unknown") at:
  • http://localhost:3000/reports/itemized_distributions
  • http://localhost:3000/reports/itemized_donations

Screenshots

[dorner]

Passes technical review - over to @awwaiid for functional.