feat: add affiliate invite rebate flow and admin rebate-rate setting

backend/migrations/131_affiliate_rebate_hardening.sql

@@ -0,0 +1,58 @@
+-- 1) Normalize historical affiliate rebate rate values.
+-- Legacy compatibility treated 0<x<=1 as fractional inputs (e.g. 0.2 => 20%).
+-- We now use pure percentage semantics, so convert persisted fractional values once.
+UPDATE settings
+SET value = to_char((value::numeric * 100), 'FM999999990.########'),
+    updated_at = NOW()
+WHERE key = 'affiliate_rebate_rate'
+  AND value ~ '^-?[0-9]+(\\.[0-9]+)?$'
+  AND value::numeric > 0
+  AND value::numeric <= 1;
+
+-- 2) Affiliate ledger for accrual/transfer traceability.
+CREATE TABLE IF NOT EXISTS user_affiliate_ledger (
+    id BIGSERIAL PRIMARY KEY,
+    user_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    action VARCHAR(32) NOT NULL,
+    amount DECIMAL(20,8) NOT NULL,
+    source_user_id BIGINT NULL REFERENCES users(id) ON DELETE SET NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_user_affiliate_ledger_user_id ON user_affiliate_ledger(user_id);
+CREATE INDEX IF NOT EXISTS idx_user_affiliate_ledger_action ON user_affiliate_ledger(action);
+
+COMMENT ON TABLE user_affiliate_ledger IS '邀请返利资金流水（累计/转入）';
+COMMENT ON COLUMN user_affiliate_ledger.action IS 'accrue|transfer';
+
+-- 3) Enforce idempotency at DB layer for payment audit actions.
+WITH ranked AS (
+    SELECT id,
+           ROW_NUMBER() OVER (PARTITION BY order_id, action ORDER BY id) AS rn
+    FROM payment_audit_logs
+)
+DELETE FROM payment_audit_logs p
+USING ranked r
+WHERE p.id = r.id
+  AND r.rn > 1;
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_payment_audit_logs_order_action_uniq
+ON payment_audit_logs(order_id, action);
+
+-- 4) Prevent retroactive affiliate rebate issuance for legacy completed balance orders.
+INSERT INTO payment_audit_logs (order_id, action, detail, operator, created_at)
+SELECT po.id::text,
+       'AFFILIATE_REBATE_SKIPPED',
+       '{"reason":"baseline before affiliate rebate idempotency rollout"}',
+       'system',
+       NOW()
+FROM payment_orders po
+WHERE po.order_type = 'balance'
+  AND po.status = 'COMPLETED'
+  AND NOT EXISTS (
+      SELECT 1
+      FROM payment_audit_logs pal
+      WHERE pal.order_id = po.id::text
+        AND pal.action IN ('AFFILIATE_REBATE_APPLIED', 'AFFILIATE_REBATE_SKIPPED')
+  );