Data and storage

MariaDB, through Battle Core's pool. Tables are created on startup.

Table	Holds
bt_tower_runs	One row per run
bt_run_stages	Stages resolved for each run
bt_stage_completions	Stage clears, used for first-run reward tracking
bt_run_rewards	Rewards paid per run
bt_factory_reward_jobs	Factory rewards waiting to be paid on the reward backend
bc_attempts (Battle Core)	Attempts, used for entry limits

Changing reward reset behavior re-reads old bt_stage_completions rows under the new rules. Nothing is migrated.