feat(ml): DQN improvements and fix downstream compilation errors
DQN changes: improved attention, ensemble networks, hindsight replay,
mixed precision, noisy layers, prioritized replay, RMSNorm, hyperopt
adapter updates, and trainer enhancements with weight_decay support.
Fix downstream crates broken by DQNConfig changes:
- trading_service: import agent::DQNConfig directly, add weight_decay field
- backtesting_service: update feature vector size 54 -> 51
- ml_training_service: convert compile-time sqlx macro to runtime query_as
- pre-commit hook: add SQLX_OFFLINE=true for DB-free compilation
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
7f53baff8f