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

backend/app/Contracts/DatabaseDriverInterface.php

@@ -24,6 +24,11 @@ interface DatabaseDriverInterface
      */
     public function getTableData(string $table, int $limit = 100, int $offset = 0): array;
 
+    /**
+     * Get the count of rows in a table.
+     */
+    public function getTableCount(string $table): int;
+
     /**
      * Get the underlying connection instance.
      */