fix: enable editing and management of hosts from included SSH config files

• Add SourceFile field to SSHHost struct to track config file origins
• Implement FindHostInAllConfigs() to locate hosts across all config files
• Fix "host not found" errors when editing/deleting hosts from included files
• Add GetAllConfigFiles() and GetAllConfigFilesFromBase() for config discovery
• Create UpdateSSHHostV2() and DeleteSSHHostV2() for cross-file operations
• Display config file source in edit and info forms for better visibility
• Add intelligent file selector for host addition when multiple configs exist
• Support -c parameter context with proper file resolution
• Exclude .backup files from Include directive processing
• Maintain backward compatibility with existing SSH config workflows

Resolves limitation where hosts from included config files could be viewed
but not edited, deleted, or properly managed through the interface.

internal/ui/view.go

@@ -35,6 +35,10 @@ func (m Model) View() string {
 		if m.helpForm != nil {
 			return m.helpForm.View()
 		}
+	case ViewFileSelector:
+		if m.fileSelectorForm != nil {
+			return m.fileSelectorForm.View()
+		}
 	case ViewList:
 		return m.renderListView()
 	}