Convert monetary/integral fields to string and switch arithmetic to BC Math to avoid floating-point errors; adjust return types to strings where appropriate (Balance, Integral, PaymentUsageTrait, IntegralPayment). Add input validation and safer comparisons in payment checks. Fix wemall logic and typos (early return for canceled/refunded orders, rename/logic fixes in UserRebate, initialize temporary $code variables, correct timestamp field name, adjust reward calculations to use bcmath, change wRebate signature). Add a database migration to enforce constraints, add new columns and indexes for wemall and payment tables. Also add business-feature documentation blocks across multiple plugin README files and update the project README.
