feat(idempotency): 为关键写接口接入幂等并完善并发容错

backend/migrations/057_add_idempotency_records.sql

@@ -0,0 +1,27 @@
+-- 幂等记录表：用于关键写接口的请求去重与结果重放
+-- 幂等执行：可重复运行
+
+CREATE TABLE IF NOT EXISTS idempotency_records (
+    id BIGSERIAL PRIMARY KEY,
+    scope VARCHAR(128) NOT NULL,
+    idempotency_key_hash VARCHAR(64) NOT NULL,
+    request_fingerprint VARCHAR(64) NOT NULL,
+    status VARCHAR(32) NOT NULL,
+    response_status INTEGER,
+    response_body TEXT,
+    error_reason VARCHAR(128),
+    locked_until TIMESTAMPTZ,
+    expires_at TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_idempotency_records_scope_key
+    ON idempotency_records (scope, idempotency_key_hash);
+
+CREATE INDEX IF NOT EXISTS idx_idempotency_records_expires_at
+    ON idempotency_records (expires_at);
+
+CREATE INDEX IF NOT EXISTS idx_idempotency_records_status_locked_until
+    ON idempotency_records (status, locked_until);
+