Adds backend/scripts/generate_test_data.py, a tool that builds a large,
prod-like RomM library (platforms, users, devices, firmware, roms with
per-provider fake metadata, saves, states, screenshots, collections, sync
data, play sessions) and bulk-inserts it for load and UI testing.
Cover/manual/screenshot path and URL columns are left empty so no asset
files are referenced.
AI assistance: written with Claude Code.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>