[adamtheturtle]

Shared target-list fixtures currently create rate-limited databases through either the running in-memory mock or a target-manager HTTP request. Move rate_limited_database into the backend plugin and reuse the typed database-creation operation already supplied to recognition-report tests. The real backend returns its configured live database.

This two-file follow-up to #3742 and #3743 advances #3738, part of #3737. Further backend decoupling remains in #3738.

Validation:

• Python 3.15: 68 target-list and recognition-report tests pass across the in-memory and Flask backends, using synthetic credentials with retries disabled. Five real-Vuforia cases are skipped locally.
• Both database-creation paths and the mock rate-limited setup are covered. The retained real-backend return branch is not exercised locally.
• Pre-commit and pre-push hooks pass, including CI partition validation, Mypy, Pyright, public type completeness, Ty, and Pyrefly. Pylint passes for both changed files, and git diff --check passes.

Full-suite coverage and real-Vuforia validation remain for hosted CI.