build_filter() silently builds an impossible range when created_after > created_before

[royalpinto007]

Problem

build_filter() with created_after > created_before silently builds an impossible Range(gte, lte) that returns empty with no error, hiding caller bugs.

Where

src/tenantq/search.py (build_filter: range condition appended without ordering check).

Acceptance

Add a failing test first asserting build_filter("acme", created_after=200, created_before=100) raises ValueError. Then fix.