fix: Update element chat config and defaults

- Update element chat default name to 'elementchat'
- Sanitize element chat name from invalid characters
- Set default namespace based on sanitized name
- Validate namespace for invalid characters
- Update documentation with new default values

examples/installers/k8s/element_chat.vsh

@@ -12,7 +12,7 @@ mut installer := element_chat.get(
 	create: true
 )!
 
-element_chat.delete()!
+// element_chat.delete()!
 
 // 2. Configure the installer (all settings are optional with sensible defaults)
 // installer.matrix_hostname = 'matrixchattest'