refactor(api): simplify instance management endpoints

- Change delete endpoint to use request body instead of path parameter
- Modify endpoint now takes field as path parameter and instance name in body
- Update README to reflect API changes
- Remove unused description field from software info
- Fix error message in auth token lookup

router.go

@@ -42,18 +42,16 @@ func setupRoutes() {
 				return
 			}
 
-			if strings.HasSuffix(remainingPath, "/delete") {
-				instanceName := strings.TrimSuffix(remainingPath, "/delete")
-				instanceName = strings.Trim(instanceName, "/")
-				DeleteInstanceHandler(w, r, instanceName)
+			if remainingPath == "delete" {
+				DeleteInstanceHandler(w, r)
 				return
 			}
 
-			if strings.Contains(remainingPath, "/modify/") {
-				parts := strings.SplitN(remainingPath, "/modify/", 2)
+			if strings.HasPrefix(remainingPath, "modify/") {
+				parts := strings.SplitN(remainingPath, "/", 2)
 				if len(parts) == 2 {
-					instanceName := strings.Trim(parts[0], "/")
-					ModifyInstanceHandler(w, r, instanceName)
+					field := parts[1]
+					ModifyInstanceHandler(w, r, field)
 					return
 				}
 			}