feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

migrations/0026_replica_heartbeat.sql

@@ -0,0 +1,38 @@
+-- Replica heartbeat: a portable read-side freshness observation for the
+-- replica fence (see crates/buzz-db/src/replica_fence.rs).
+--
+-- Why: the fence's ordered writer-side proof previously ended in a WAL-LSN
+-- comparison (`pg_last_wal_replay_lsn() >= L`), which Aurora's reader
+-- endpoints do not expose — the fence therefore never opened on Aurora, by
+-- design (fail closed). This table replaces only that read-side observation:
+-- the probe commits a monotonically increasing `token` AFTER the ordered
+-- writer scan (clock sample -> oldest-xact guard), and a reader session that
+-- observes token >= M has, by WAL/storage replay order, also replayed every
+-- commit that preceded M. The commit-time floor guard (migration 0021) and
+-- the writer-side scan remain load-bearing and unchanged.
+--
+-- Shape: exactly one row, enforced by the CHECK'd primary key. Every relay
+-- pod's probe increments the same row; the single-row UPDATE is the
+-- serialization point that makes tokens globally commit-ordered, which is
+-- what lets a pod prove coverage from the greatest token it retained that is
+-- <= the token a reader session observes (multi-pod safety).
+--
+-- `epoch` detects resets: a restore/re-seed that rolls `token` backwards
+-- must never let a stale retained token masquerade as fresh coverage.
+-- Readers validate the observed epoch against the epoch retained with each
+-- token; a mismatch fails closed (route to writer).
+--
+-- Not an events row: exempt from the created_at floor guard by construction,
+-- and deliberately deployment-global (no community_id) — it describes the
+-- replication topology, not tenant data.
+
+CREATE TABLE replica_heartbeat (
+    id    smallint PRIMARY KEY CHECK (id = 1),
+    epoch uuid     NOT NULL DEFAULT gen_random_uuid(),
+    token bigint   NOT NULL DEFAULT 0
+);
+
+INSERT INTO replica_heartbeat (id) VALUES (1);
+
+INSERT INTO _operator_global_tables (table_name, reason) VALUES
+    ('replica_heartbeat', 'single-row replication freshness token; describes deployment topology, never tenant data');