docs: use example.com hostnames instead of private IPs in FDW examples

Keeps the repo free of any private-IP patterns (consistent with the pre-commit
secret guard) and reads as clearer documentation placeholders.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: programmerShinobi

docs/04-EXTENSIONS.md

@@ -25,7 +25,7 @@ Quick taste:
 
 ```sql
 CREATE SERVER remote_pg FOREIGN DATA WRAPPER postgres_fdw
-    OPTIONS (host '10.0.0.10', port '5432', dbname 'remote_db');
+    OPTIONS (host 'remote-postgres.example.com', port '5432', dbname 'remote_db');
 CREATE USER MAPPING FOR CURRENT_USER SERVER remote_pg
     OPTIONS (user 'remote_user', password 'secret');
 IMPORT FOREIGN SCHEMA public FROM SERVER remote_pg INTO public;

scripts/fdw-examples/mysql_fdw.sql

@@ -4,7 +4,7 @@
 
 CREATE SERVER IF NOT EXISTS remote_mysql
     FOREIGN DATA WRAPPER mysql_fdw
-    OPTIONS (host '10.0.0.20', port '3306');
+    OPTIONS (host 'remote-mysql.example.com', port '3306');
 
 CREATE USER MAPPING IF NOT EXISTS FOR CURRENT_USER
     SERVER remote_mysql

scripts/fdw-examples/postgres_fdw.sql

@@ -6,7 +6,7 @@
 -- 1) Define the remote server.
 CREATE SERVER IF NOT EXISTS remote_pg
     FOREIGN DATA WRAPPER postgres_fdw
-    OPTIONS (host '10.0.0.10', port '5432', dbname 'remote_db');
+    OPTIONS (host 'remote-postgres.example.com', port '5432', dbname 'remote_db');
 
 -- 2) Map your local user to a remote login.
 CREATE USER MAPPING IF NOT EXISTS FOR CURRENT_USER