Fix count SQL semicolon trimming

[Aias00]

Summary

• trim generated count SQL using its own length instead of the original SQL length
• reuse the same trailing-semicolon helper for fallback count SQL wrapping
• add focused SqlUtils tests for count SQL semicolon handling

Verification

• mvn -B -f chat2db-community-server/pom.xml -pl :chat2db-community-spi -am -Dmaven.test.skip=false -DskipTests=false -Dtest=SqlUtilsTest -Dsurefire.failIfNoSpecifiedTests=false -Dmaven.test.failure.ignore=false test
• mvn -B -f chat2db-community-server/pom.xml -pl :chat2db-community-spi -am -Dmaven.test.skip=true package

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[Aias00]

close: #1970