fix: preserve zero values in number fields

[RabbiIslamRony]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Security fix
• Improvement
• New Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Text changes
• Other... Please describe:

Description

Issue

A custom Number field value of 0 was treated as empty in multiple submission paths, so the metadata was removed instead of saved. The search request also used PHP's default array_filter(), which removed the string value "0"; as a result, an exact search for zero ran without the intended number-field meta query.

Fix

• Distinguish a genuinely blank Number field from an explicit numeric zero before sanitizing.
• Preserve numeric zero in the current submission controller, legacy submission path, and admin/metabox metadata filtering.
• Preserve "0" in custom-field search requests and repopulate it in the search UI.
• Keep the existing behavior for blank optional fields, exact nonzero number searches, text partial matching, and number ranges.

Test cases

1. Submit a new listing with the custom Number field set to 0; confirm the metadata exists and is stored as zero.
2. Edit the value from 0 to 2.50, then back to 0; confirm each value is preserved.
3. Clear the optional Number field; confirm its metadata is deleted rather than converted to zero.
4. Submit a new listing with the optional Number field blank; confirm no zero metadata is created.
5. Search the Number field for 0; confirm only the zero-valued listing is returned and the query value is retained.
6. Search the Number field for 2; confirm the listing with 3 is not returned.
7. Search the Number field with the 2-3 range; confirm both boundary values are returned.
8. Verify the exact-zero and range result layouts on desktop and mobile and confirm no horizontal overflow or visible listing-card regression.

Any linked issues

• TeamSync support ticket: https://team.sovware.com/support/directorist/3285

Checklist

• My code follows the WordPress coding standards