WKBCH-18: Change startTime column type to Int64

Store timestamps as epoch milliseconds (Int64) instead of DateTime64(3)
for consistent handling across ingest, storage, and offsets tables.

Author: dvasilas

templates/clickhouse/init.d/02-create-ingest-table.sql

@@ -5,7 +5,7 @@ CREATE TABLE IF NOT EXISTS logs.access_logs_ingest
     hostname               LowCardinality(Nullable(String)),
 
     -- AWS access server logs fields https://docs.aws.amazon.com/AmazonS3/latest/userguide/LogFormat.html
-    startTime              DateTime64(3), -- AWS "Time" field
+    startTime              Int64, -- AWS "Time" field (epoch milliseconds)
     requester              Nullable(String),
     operation              Nullable(String),
     requestURI             Nullable(String),

templates/clickhouse/init.d/03-create-storage-table.sql

@@ -5,7 +5,7 @@ CREATE TABLE IF NOT EXISTS logs.access_logs
     hostname               LowCardinality(Nullable(String)),
 
     -- AWS access server logs fields https://docs.aws.amazon.com/AmazonS3/latest/userguide/LogFormat.html
-    startTime              DateTime64(3), -- AWS "Time" field
+    startTime              Int64, -- AWS "Time" field (epoch milliseconds)
     requester              Nullable(String),
     operation              Nullable(String),
     requestURI             Nullable(String),

templates/clickhouse/init.d/04-create-offsets-table.sql

@@ -3,7 +3,7 @@ CREATE TABLE IF NOT EXISTS logs.offsets
     bucketName                String,
     raftSessionID             UInt16,
     lastProcessedInsertedAt   DateTime,
-    lastProcessedStartTime    DateTime64(3),
+    lastProcessedStartTime    Int64,
     lastProcessedReqId        String
 )
 ENGINE = ReplacingMergeTree(lastProcessedInsertedAt)