fix: use lagInFrame instead of lag for ClickHouse compatibility

ClickHouse does not have lag() as a window function. Use lagInFrame()
with explicit ROWS BETWEEN frame instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/storage/ClickHouseMetricsQueryStore.java

@@ -88,8 +88,9 @@ public class ClickHouseMetricsQueryStore implements MetricsQueryStore {
 
         String finalSql = """
             SELECT bucket, metric_name,
-                   greatest(0, max_val - lag(max_val, 1, max_val)
-                       OVER (PARTITION BY metric_name ORDER BY bucket)) AS avg_value
+                   greatest(0, max_val - lagInFrame(max_val, 1, max_val)
+                       OVER (PARTITION BY metric_name ORDER BY bucket
+                       ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)) AS avg_value
             FROM (
                 SELECT toStartOfInterval(collected_at, INTERVAL %d SECOND) AS bucket,
                        metric_name,