fix(stats): close 8 ClickHouseStatsStoreIT TZ failures (bucket DateTime('UTC') + JVM UTC pin)

Two-layer fix for the TZ drift that caused stats reads to miss every row
when the JVM default TZ and CH session TZ disagreed:

- Insert side: ClickHouse JDBC 0.9.7 formats java.sql.Timestamp via
  Timestamp.toString(), which uses JVM default TZ. A CEST JVM shipping
  to a UTC CH server stored Unix timestamps off by the TZ offset (the
  triage report's original symptom). Pinned JVM default to UTC in
  CameleerServerApplication.main() — standard practice for observability
  servers that push to time-series stores.
- Read side: stats_1m_* tables now declare bucket as DateTime('UTC'),
  MV SELECTs wrap toStartOfMinute(start_time) in toDateTime(..., 'UTC')
  so projections match column type, and ClickHouseStatsStore.lit(Instant)
  emits toDateTime('...', 'UTC') rather than a bare literal — defence
  in depth against future refactors.

Test class pins its own JVM TZ (the store IT builds its own
HikariDataSource, bypassing the main() path). Debug scaffolding from
the triage investigation removed.

Greenfield CH — no migration needed.

Verified: 14/14 ClickHouseStatsStoreIT green, plus 84/84 across all
ClickHouse IT classes (no regression from the JVM TZ default change).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/resources/clickhouse/init.sql

@@ -132,7 +132,7 @@ SETTINGS index_granularity = 8192;
 
 CREATE TABLE IF NOT EXISTS stats_1m_all (
     tenant_id     LowCardinality(String),
-    bucket        DateTime,
+    bucket        DateTime('UTC'),
     environment   LowCardinality(String) DEFAULT 'default',
     total_count   AggregateFunction(uniq, String),
     failed_count  AggregateFunction(uniqIf, String, UInt8),
@@ -149,7 +149,7 @@ TTL bucket + INTERVAL 365 DAY DELETE;
 CREATE MATERIALIZED VIEW IF NOT EXISTS stats_1m_all_mv TO stats_1m_all AS
 SELECT
     tenant_id,
-    toStartOfMinute(start_time)           AS bucket,
+    toDateTime(toStartOfMinute(start_time), 'UTC') AS bucket,
     environment,
     uniqState(execution_id)               AS total_count,
     uniqIfState(execution_id, status = 'FAILED') AS failed_count,
@@ -165,7 +165,7 @@ GROUP BY tenant_id, bucket, environment;
 CREATE TABLE IF NOT EXISTS stats_1m_app (
     tenant_id      LowCardinality(String),
     application_id LowCardinality(String),
-    bucket         DateTime,
+    bucket         DateTime('UTC'),
     environment    LowCardinality(String) DEFAULT 'default',
     total_count    AggregateFunction(uniq, String),
     failed_count   AggregateFunction(uniqIf, String, UInt8),
@@ -183,7 +183,7 @@ CREATE MATERIALIZED VIEW IF NOT EXISTS stats_1m_app_mv TO stats_1m_app AS
 SELECT
     tenant_id,
     application_id,
-    toStartOfMinute(start_time)           AS bucket,
+    toDateTime(toStartOfMinute(start_time), 'UTC') AS bucket,
     environment,
     uniqState(execution_id)               AS total_count,
     uniqIfState(execution_id, status = 'FAILED') AS failed_count,
@@ -200,7 +200,7 @@ CREATE TABLE IF NOT EXISTS stats_1m_route (
     tenant_id      LowCardinality(String),
     application_id LowCardinality(String),
     route_id       LowCardinality(String),
-    bucket         DateTime,
+    bucket         DateTime('UTC'),
     environment    LowCardinality(String) DEFAULT 'default',
     total_count    AggregateFunction(uniq, String),
     failed_count   AggregateFunction(uniqIf, String, UInt8),
@@ -219,7 +219,7 @@ SELECT
     tenant_id,
     application_id,
     route_id,
-    toStartOfMinute(start_time)           AS bucket,
+    toDateTime(toStartOfMinute(start_time), 'UTC') AS bucket,
     environment,
     uniqState(execution_id)               AS total_count,
     uniqIfState(execution_id, status = 'FAILED') AS failed_count,
@@ -236,7 +236,7 @@ CREATE TABLE IF NOT EXISTS stats_1m_processor (
     tenant_id      LowCardinality(String),
     application_id LowCardinality(String),
     processor_type LowCardinality(String),
-    bucket         DateTime,
+    bucket         DateTime('UTC'),
     environment    LowCardinality(String) DEFAULT 'default',
     total_count    AggregateFunction(uniq, String),
     failed_count   AggregateFunction(uniqIf, String, UInt8),
@@ -254,7 +254,7 @@ SELECT
     tenant_id,
     application_id,
     processor_type,
-    toStartOfMinute(start_time)           AS bucket,
+    toDateTime(toStartOfMinute(start_time), 'UTC') AS bucket,
     environment,
     uniqState(concat(execution_id, toString(seq))) AS total_count,
     uniqIfState(concat(execution_id, toString(seq)), status = 'FAILED') AS failed_count,
@@ -272,7 +272,7 @@ CREATE TABLE IF NOT EXISTS stats_1m_processor_detail (
     route_id       LowCardinality(String),
     processor_id   String,
     processor_type LowCardinality(String),
-    bucket         DateTime,
+    bucket         DateTime('UTC'),
     environment    LowCardinality(String) DEFAULT 'default',
     total_count    AggregateFunction(uniq, String),
     failed_count   AggregateFunction(uniqIf, String, UInt8),
@@ -292,7 +292,7 @@ SELECT
     route_id,
     processor_id,
     processor_type,
-    toStartOfMinute(start_time)           AS bucket,
+    toDateTime(toStartOfMinute(start_time), 'UTC') AS bucket,
     environment,
     uniqState(concat(execution_id, toString(seq))) AS total_count,
     uniqIfState(concat(execution_id, toString(seq)), status = 'FAILED') AS failed_count,