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

backend/app/Services/Database/MySqlDriver.php

@@ -69,6 +69,12 @@ class MySqlDriver implements DatabaseDriverInterface, SchemaDiscoveryInterface
         return $this->query("SELECT * FROM `{$table}` LIMIT ? OFFSET ?", [$limit, $offset]);
     }
 
+    public function getTableCount(string $table): int
+    {
+        $result = $this->query("SELECT COUNT(*) as count FROM `{$table}`");
+        return (int) ($result[0]->count ?? 0);
+    }
+
     public function getForeignKeys(string $table): array
     {
         $sql = "