Add IntOrFalse type to handle polymorphic API responses

Kanboard API returns int (ID) on success and false (bool) on failure
for create operations. Add IntOrFalse type that handles both cases
and update CreateTask, CreateComment, CreateTag, CreateTaskFile, and
CreateTaskLink to use it.

comments.go

@@ -42,7 +42,7 @@ func (c *Client) CreateComment(ctx context.Context, taskID, userID int, content
 		"content": content,
 	}
 
-	var commentID int
+	var commentID IntOrFalse
 	if err := c.call(ctx, "createComment", params, &commentID); err != nil {
 		return nil, fmt.Errorf("createComment: %w", err)
 	}
@@ -52,7 +52,7 @@ func (c *Client) CreateComment(ctx context.Context, taskID, userID int, content
 	}
 
 	// Fetch the created comment to return full details
-	return c.GetComment(ctx, commentID)
+	return c.GetComment(ctx, int(commentID))
 }
 
 // UpdateComment updates the content of a comment.

files.go

@@ -29,7 +29,7 @@ func (c *Client) CreateTaskFile(ctx context.Context, projectID, taskID int, file
 		"blob":       base64.StdEncoding.EncodeToString(content),
 	}
 
-	var result int
+	var result IntOrFalse
 	if err := c.call(ctx, "createTaskFile", params, &result); err != nil {
 		return 0, fmt.Errorf("createTaskFile: %w", err)
 	}
@@ -38,7 +38,7 @@ func (c *Client) CreateTaskFile(ctx context.Context, projectID, taskID int, file
 		return 0, fmt.Errorf("createTaskFile: failed to upload file")
 	}
 
-	return result, nil
+	return int(result), nil
 }
 
 // DownloadTaskFile downloads a file's content by its ID.

links.go

@@ -27,7 +27,7 @@ func (c *Client) CreateTaskLink(ctx context.Context, taskID, oppositeTaskID, lin
 		"link_id":          linkID,
 	}
 
-	var result int
+	var result IntOrFalse
 	if err := c.call(ctx, "createTaskLink", params, &result); err != nil {
 		return 0, fmt.Errorf("createTaskLink: %w", err)
 	}
@@ -36,7 +36,7 @@ func (c *Client) CreateTaskLink(ctx context.Context, taskID, oppositeTaskID, lin
 		return 0, fmt.Errorf("createTaskLink: failed to create link")
 	}
 
-	return result, nil
+	return int(result), nil
 }
 
 // RemoveTaskLink deletes a task link.

tags.go

@@ -75,11 +75,11 @@ func (c *Client) CreateTag(ctx context.Context, projectID int, name, colorID str
 		params["color_id"] = colorID
 	}
 
-	var result int
+	var result IntOrFalse
 	if err := c.call(ctx, "createTag", params, &result); err != nil {
 		return 0, fmt.Errorf("createTag: %w", err)
 	}
-	return result, nil
+	return int(result), nil
 }
 
 // UpdateTag updates an existing tag's name and/or color.

tasks.go

@@ -41,7 +41,7 @@ func (c *Client) GetAllTasks(ctx context.Context, projectID int, status TaskStat
 
 // CreateTask creates a new task and returns the created task.
 func (c *Client) CreateTask(ctx context.Context, req CreateTaskRequest) (*Task, error) {
-	var taskID int
+	var taskID IntOrFalse
 	if err := c.call(ctx, "createTask", req, &taskID); err != nil {
 		return nil, fmt.Errorf("createTask: %w", err)
 	}
@@ -51,7 +51,7 @@ func (c *Client) CreateTask(ctx context.Context, req CreateTaskRequest) (*Task,
 	}
 
 	// Fetch the created task to return full details
-	return c.GetTask(ctx, taskID)
+	return c.GetTask(ctx, int(taskID))
 }
 
 // UpdateTask updates an existing task.

types.go

@@ -2,6 +2,7 @@ package kanboard
 
 import (
 	"encoding/json"
+	"fmt"
 	"strconv"
 )
 
@@ -105,6 +106,33 @@ func (i *StringInt64) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// IntOrFalse is an int that can be unmarshaled from a JSON int or false.
+// Kanboard API returns false on failure, int (ID) on success for create operations.
+type IntOrFalse int
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (i *IntOrFalse) UnmarshalJSON(data []byte) error {
+	// Try as int first (success case)
+	var n int
+	if err := json.Unmarshal(data, &n); err == nil {
+		*i = IntOrFalse(n)
+		return nil
+	}
+
+	// Try as bool (failure case: false)
+	var b bool
+	if err := json.Unmarshal(data, &b); err == nil {
+		if b {
+			*i = 1 // true shouldn't happen, but handle it
+		} else {
+			*i = 0
+		}
+		return nil
+	}
+
+	return fmt.Errorf("cannot unmarshal %s into IntOrFalse", data)
+}
+
 // Project represents a Kanboard project (board).
 type Project struct {
 	ID                  StringInt  `json:"id"`

types_test.go

@@ -97,6 +97,31 @@ func TestStringInt64_UnmarshalJSON(t *testing.T) {
 	}
 }
 
+func TestIntOrFalse_UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"int value", `42`, 42},
+		{"int zero", `0`, 0},
+		{"false", `false`, 0},
+		{"true", `true`, 1},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var i IntOrFalse
+			if err := json.Unmarshal([]byte(tt.input), &i); err != nil {
+				t.Fatalf("unmarshal error: %v", err)
+			}
+			if int(i) != tt.expected {
+				t.Errorf("expected %v, got %v", tt.expected, i)
+			}
+		})
+	}
+}
+
 func TestProject_UnmarshalJSON(t *testing.T) {
 	jsonData := `{
 		"id": "1",