refactor: use environment variables for Tryton credentials

AGENTS.md

@@ -66,17 +66,24 @@ fastmcp run tryton_mcp.server
 
 ## Configuration
 
-Edit `TRYTON_CREDENTIALS` in `server.py:12-17` to change connection settings:
+Credentials are loaded from environment variables (with sensible defaults):
 
-```python
-TRYTON_CREDENTIALS = {
-    "hostname": 'dev.naliia.co',
-    "database": 'capacitacion',
-    "username": 'admin',
-    "password": 'admin' 
-}
+```bash
+export TRYTON_HOSTNAME=dev.naliia.co
+export TRYTON_DATABASE=capacitacion
+export TRYTON_USERNAME=admin
+export TRYTON_PASSWORD=admin
+export TRYTON_PORT=8000
 ```
 
+Or copy `.env.example` to `.env` and adjust values:
+
+```bash
+cp .env.example .env
+```
+
+Note: `.env` is gitignored to protect credentials.
+
 ## Testing RPC Calls
 
 Use `test_rpc.py` to test Tryton RPC calls independently: