perf: sync protocol and core hardening updates

deploy/migrations/0066_dispatch_outbox_user_lanes.up.sql

@@ -0,0 +1,39 @@
+-- 一条 durable user update 只能有一个在线投递任务。历史 schema 的
+-- ON CONFLICT DO NOTHING 没有对应唯一键，先显式保留最早任务并删除重复项。
+WITH duplicates AS (
+    SELECT id
+    FROM (
+        SELECT
+            id,
+            row_number() OVER (
+                PARTITION BY target_user_id, pts
+                -- 若历史重复中仍有可投递任务，优先保留它；不能让一个更早的
+                -- failed 副本覆盖健康 pending 副本并人为阻塞该用户 lane。
+                ORDER BY
+                    CASE status
+                        WHEN 'pending' THEN 0
+                        WHEN 'dispatching' THEN 1
+                        ELSE 2
+                    END,
+                    id ASC
+            ) AS rn
+        FROM dispatch_outbox
+    ) ranked
+    WHERE ranked.rn > 1
+)
+DELETE FROM dispatch_outbox d
+USING duplicates x
+WHERE d.id = x.id;
+
+CREATE UNIQUE INDEX dispatch_outbox_user_pts_uidx
+    ON dispatch_outbox (target_user_id, pts);
+
+-- ClaimDispatchOutboxShards 固定用 256 logical shards；表达式必须与查询
+-- 完全一致，避免每个 worker 为筛自己的 lane 全表扫描。
+CREATE INDEX dispatch_outbox_logical_shard_head_idx
+    ON dispatch_outbox (
+        mod(target_user_id, 256::bigint),
+        target_user_id,
+        pts,
+        id
+    );