Fix sqlite_import() failing when tables already exist

sqlite3 .dump produces 'CREATE TABLE' without 'IF NOT EXISTS', so
importing the dump back into the same database fails with
"table X already exists" and exit code 1.

Add a regex replacement to insert 'IF NOT EXISTS' into CREATE TABLE
statements from the dump, consistent with the existing handling for
CREATE INDEX statements.

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>

Author: Copilot

src/DB_Command_SQLite.php

@@ -424,6 +424,7 @@ protected function sqlite_import( $file, $assoc_args ) {
 
 		// Ignore errors about unique constraints and existing indexes.
 		$contents = str_replace( 'INSERT INTO', 'INSERT OR IGNORE INTO', $contents );
+		$contents = preg_replace( '/\bCREATE TABLE (?!IF NOT EXISTS\b)/i', 'CREATE TABLE IF NOT EXISTS ', $contents );
 		$contents = str_replace( 'CREATE INDEX "', 'CREATE INDEX IF NOT EXISTS "', $contents );
 		$contents = str_replace( 'CREATE UNIQUE INDEX "', 'CREATE UNIQUE INDEX IF NOT EXISTS "', $contents );