Implement Maintenance trainer card

[bcollazo]

Summary

• implement Maintenance (B2b 066) move generation with the correct post-play hand-size requirement
• add Maintenance effect resolution by selecting 2 cards from hand to shuffle into deck, then drawing 1
• add a shared stack action for shuffling chosen hand cards into deck and cover the new trainer behavior with a unit test

Verification

• cargo fmt
• cargo clippy --fix --allow-dirty -- -D warnings
• cargo test --features tui,test-utils
• cargo run --bin card_test -- "B2b 066"