Add 5-minute AggregatingMergeTree stats rollup for dashboard queries

Pre-aggregate route execution stats into 5-minute buckets using a
materialized view with -State/-Merge combinators. Rewrite stats() and
timeseries() to query the rollup table instead of scanning the wide
base table. Active count remains a real-time query since RUNNING is
transient. Includes idempotent backfill migration.

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

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

@@ -0,0 +1,31 @@
+-- Pre-aggregated 5-minute stats rollup for route executions.
+-- 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 (
+    bucket            DateTime('UTC'),
+    route_id          LowCardinality(String),
+    agent_id          LowCardinality(String),
+    total_count       AggregateFunction(count, UInt64),
+    failed_count      AggregateFunction(countIf, UInt8),
+    duration_sum      AggregateFunction(sum, UInt64),
+    p99_duration      AggregateFunction(quantileTDigest(0.99), UInt64)
+)
+ENGINE = AggregatingMergeTree()
+PARTITION BY toYYYYMMDD(bucket)
+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
+TO route_execution_stats_5m
+AS SELECT
+    toStartOfFiveMinutes(start_time) AS bucket,
+    route_id,
+    agent_id,
+    countState()                            AS total_count,
+    countIfState(status = 'FAILED')         AS failed_count,
+    sumState(duration_ms)                   AS duration_sum,
+    quantileTDigestState(0.99)(duration_ms) AS p99_duration
+FROM route_executions
+GROUP BY bucket, route_id, agent_id;

cameleer3-server-app/src/main/resources/clickhouse/08-stats-rollup-backfill.sql

@@ -0,0 +1,16 @@
+-- One-time idempotent backfill of existing route_executions into the
+-- 5-minute stats rollup table. Safe for repeated execution — the WHERE
+-- clause skips the INSERT if the target table already contains data.
+
+INSERT INTO route_execution_stats_5m
+SELECT
+    toStartOfFiveMinutes(start_time) AS bucket,
+    route_id,
+    agent_id,
+    countState()                            AS total_count,
+    countIfState(status = 'FAILED')         AS failed_count,
+    sumState(duration_ms)                   AS duration_sum,
+    quantileTDigestState(0.99)(duration_ms) AS p99_duration
+FROM route_executions
+WHERE (SELECT count() FROM route_execution_stats_5m) = 0
+GROUP BY bucket, route_id, agent_id;