fix: Ensure strict typing for input defaults to prevent runtime errors

core/src/main/java/io/kestra/core/models/flows/Input.java

@@ -78,7 +78,7 @@ public abstract class Input<T> implements Data {
     @Schema(
         title = "The default value to use if no value is specified."
     )
-    Object defaults;
+    T defaults;
 
     @Schema(
         title = "The display name of the input."

core/src/main/java/io/kestra/core/runners/FlowInputOutput.java

@@ -404,10 +404,10 @@ private Object parseType(Execution execution, Type type, String id, Type element
                 // Assuming that after the render we must have a double/int, so we can safely use its toString representation
                 case FLOAT -> current instanceof Float ? current : Float.valueOf(current.toString());
                 case BOOLEAN -> current instanceof Boolean ? current : Boolean.valueOf((String) current);
-                case DATETIME -> Instant.parse(((String) current));
-                case DATE -> LocalDate.parse(((String) current));
-                case TIME -> LocalTime.parse(((String) current));
-                case DURATION -> Duration.parse(((String) current));
+                case DATETIME -> current instanceof Instant ? current : Instant.parse(((String) current));
+                case DATE -> current instanceof LocalDate ? current : LocalDate.parse(((String) current));
+                case TIME -> current instanceof LocalTime ? current : LocalTime.parse(((String) current));
+                case DURATION -> current instanceof Duration ? current : Duration.parse(((String) current));
                 case FILE -> {
                     URI uri = URI.create(((String) current).replace(File.separator, "/"));