Apply two-sided bid-ask spread so BYC par sits inside the book

[hoffmang9]

Summary

• Two-sided markets now apply strategy_target_spread_bps as a full bid-ask around mid (buy below, sell above) via MarketConfig::quote_price_for_side.
• byc_two_sided_wusdbc is mid 1.0 + 20 bps, so 1.0 sits inside the book (bid 0.999 / ask 1.001).
• Sell-only configs omit the unused field; PlannedAction / StrategyConfig no longer carry dead target_spread_bps.

Test plan

• Unit tests: spread math, two-sided vs sell-only, offer terms, unique-maker buy clip, reservation amounts
• Rebuild and restart greenfloord on john-deere
• After listing expiry (~30 min), confirm Dexie BYC/wUSDC.b quotes at 0.999 bid / 1.001 ask