feat: make Todoist optional, guard nil client calls

TODOIST_API_KEY is no longer required — native task management works
without it. Guards nil todoistClient in handleAtomToggle.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2 files changed, 5 insertions, 5 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 67658b4..6d2e2ef 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -109,11 +109,7 @@ func Load() (*Config, error) {
 
 // Validate checks that required configuration is present
 func (c *Config) Validate() error {
-	// Require both Todoist and Trello (primary task management systems)
-	if c.TodoistAPIKey == "" {
-		return fmt.Errorf("TODOIST_API_KEY is required")
-	}
-
+	// Todoist is optional — native task management replaces it when key is absent
 	if c.TrelloAPIKey == "" {
 		return fmt.Errorf("TRELLO_API_KEY is required")
 	}
diff --git a/internal/handlers/handlers.go b/internal/handlers/handlers.go
index 877293a..5ecaf7c 100644
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -612,6 +612,10 @@ func (h *Handler) handleAtomToggle(w http.ResponseWriter, r *http.Request, compl
 			err = h.store.UncompleteNativeTask(id)
 		}
 	case "todoist":
+		if h.todoistClient == nil {
+			JSONError(w, http.StatusServiceUnavailable, "Todoist not configured", nil)
+			return
+		}
 		if complete {
 			err = h.todoistClient.CompleteTask(ctx, id)
 		} else {