feat: define SchemaDiscoveryInterface for database schema inspection

backend/app/Contracts/SchemaDiscoveryInterface.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Contracts;
+
+interface SchemaDiscoveryInterface
+{
+    /**
+     * List all databases.
+     */
+    public function getDatabases(): array;
+
+    /**
+     * List all tables in the current database.
+     */
+    public function getTables(): array;
+
+    /**
+     * Get the schema of a specific table.
+     */
+    public function getTableSchema(string $table): array;
+
+    /**
+     * Get foreign keys for a table.
+     */
+    public function getForeignKeys(string $table): array;
+}