fix: schema initializer skips comment-only SQL segments

The V4 DDL had a semicolon inside a comment which caused the
split-on-semicolon logic to produce a comment-only segment that
ClickHouse rejected as empty query. Fixed the comment and made
the initializer strip comment-only segments before execution.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/config/ClickHouseSchemaInitializer.java

@@ -42,7 +42,13 @@ public class ClickHouseSchemaInitializer {
                 log.info("Executing ClickHouse schema script: {}", script.getFilename());
                 for (String statement : sql.split(";")) {
                     String trimmed = statement.trim();
-                    if (!trimmed.isEmpty()) {
+                    // Skip empty segments and comment-only segments
+                    String withoutComments = trimmed.lines()
+                            .filter(line -> !line.stripLeading().startsWith("--"))
+                            .map(String::trim)
+                            .filter(line -> !line.isEmpty())
+                            .reduce("", (a, b) -> a + b);
+                    if (!withoutComments.isEmpty()) {
                         clickHouseJdbc.execute(trimmed);
                     }
                 }

cameleer3-server-app/src/main/resources/clickhouse/V4__stats_tables_and_mvs.sql

@@ -1,6 +1,6 @@
 -- V4__stats_tables_and_mvs.sql
 -- Materialized views replacing TimescaleDB continuous aggregates.
--- Tables use AggregatingMergeTree; MVs use -State combinators.
+-- Tables use AggregatingMergeTree, MVs use -State combinators.
 
 -- stats_1m_all (global)