feat: import Chinese-localized Buzz source snapshot

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

migrations/0024_event_ttl_refresh_shared_lock.sql

@@ -0,0 +1,58 @@
+-- T1a repair: the 0022 trigger takes FOR UPDATE on the channel row before
+-- testing ttl_seconds, so every durable message in a PERMANENT channel
+-- serializes on that tuple at commit time (deferred trigger) — one hot
+-- channel means fully serialized commits, each holding the lock across its
+-- WAL flush. Observed live at 200 QPS: commit latency 0.07ms -> ~15ms,
+-- non-CPU DB load ~9/vCPU with CPU under 45%.
+--
+-- Repair keeps 0022's stale-prefetch proof but moves the synchronization to
+-- a per-channel advisory lock, shared on the hot path:
+--   * Event insert: shared channel-key lock -> read ttl_seconds. NULL returns
+--     with no tuple lock and no update; shared locks admit each other, so
+--     permanent-channel commits proceed concurrently.
+--   * Permanent->ephemeral (or TTL-change) transition (update_channel in
+--     crates/buzz-db/src/channel.rs) takes the same key EXCLUSIVE before its
+--     UPDATE. Either the transition commits first and the event's read sees
+--     the TTL (and refreshes), or the event commits first and the
+--     transition's own deadline reset is later than anything the event would
+--     have written. No stale-NULL hole in either order.
+--   * Ephemeral channels still run the conditional UPDATE; their row updates
+--     serialize per channel, but only ephemeral channels pay that.
+-- Lock key domain 'buzz_channel_ttl:' is distinct from 'buzz_push_gate:'
+-- (migration 0023) and the audit/lease lock families. Lock order note: the
+-- deferred trigger acquires this key at COMMIT, after any push-gate shared
+-- lock taken during insert; no path acquires both domains exclusively.
+CREATE OR REPLACE FUNCTION refresh_channel_ttl_after_event_insert() RETURNS trigger
+LANGUAGE plpgsql AS $$
+DECLARE
+    channel_ttl INTEGER;
+BEGIN
+    -- Kind 9007 creates the channel and initializes its deadline itself.
+    IF NEW.channel_id IS NOT NULL AND NEW.kind <> 9007 THEN
+        BEGIN
+            PERFORM pg_advisory_xact_lock_shared(hashtextextended(
+                'buzz_channel_ttl:' || NEW.community_id::text || ':' || NEW.channel_id::text, 0));
+
+            SELECT ttl_seconds INTO channel_ttl
+            FROM channels
+            WHERE community_id = NEW.community_id AND id = NEW.channel_id;
+
+            IF channel_ttl IS NOT NULL THEN
+                UPDATE channels
+                SET ttl_deadline = clock_timestamp() + make_interval(secs => ttl_seconds)
+                WHERE community_id = NEW.community_id
+                  AND id = NEW.channel_id
+                  AND ttl_seconds IS NOT NULL
+                  AND archived_at IS NULL
+                  AND deleted_at IS NULL;
+            END IF;
+        EXCEPTION WHEN OTHERS THEN
+            -- Preserve the existing best-effort contract: a TTL refresh failure
+            -- must not reject an otherwise valid durable event.
+            RAISE WARNING 'channel TTL refresh failed for community %, channel %: %',
+                NEW.community_id, NEW.channel_id, SQLERRM;
+        END;
+    END IF;
+    RETURN NULL;
+END
+$$;