Fix stats rollup: AggregateFunction(count) takes no type argument

ClickHouse count() accepts no arguments, so the column type must be
AggregateFunction(count) not AggregateFunction(count, UInt64). The
latter causes countMerge() to fail with ILLEGAL_TYPE_OF_ARGUMENT.
Drop and recreate the table/MV to apply the corrected schema.

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

cameleer3-server-app/src/main/resources/clickhouse/07-stats-rollup.sql

@@ -2,11 +2,15 @@
 -- Uses AggregatingMergeTree with -State/-Merge combinators so intermediate
 -- aggregates can be merged across arbitrary time windows and dimensions.
 
-CREATE TABLE IF NOT EXISTS route_execution_stats_5m (
+-- Drop existing objects to allow schema changes (MV must be dropped before table)
+DROP VIEW IF EXISTS route_execution_stats_5m_mv;
+DROP TABLE IF EXISTS route_execution_stats_5m;
+
+CREATE TABLE route_execution_stats_5m (
     bucket            DateTime('UTC'),
     route_id          LowCardinality(String),
     agent_id          LowCardinality(String),
-    total_count       AggregateFunction(count, UInt64),
+    total_count       AggregateFunction(count),
     failed_count      AggregateFunction(countIf, UInt8),
     duration_sum      AggregateFunction(sum, UInt64),
     p99_duration      AggregateFunction(quantileTDigest(0.99), UInt64)
@@ -17,7 +21,7 @@ ORDER BY (agent_id, route_id, bucket)
 TTL bucket + toIntervalDay(30)
 SETTINGS ttl_only_drop_parts = 1;
 
-CREATE MATERIALIZED VIEW IF NOT EXISTS route_execution_stats_5m_mv
+CREATE MATERIALIZED VIEW route_execution_stats_5m_mv
 TO route_execution_stats_5m
 AS SELECT
     toStartOfFiveMinutes(start_time) AS bucket,