feat: initialize backend database service architecture and implement frontend schema explorer components

backend/app/Services/DatabaseService.php

@@ -82,4 +82,12 @@ class DatabaseService
     {
         return $this->getDriver()->getTableData($table, $limit, $offset);
     }
+
+    /**
+     * Get table row count.
+     */
+    public function getTableCount(string $table): int
+    {
+        return $this->getDriver()->getTableCount($table);
+    }
 }