feat: native task management + Todoist migration

Adds doot-owned task storage (native_tasks table) so tasks can be
managed without Todoist. CompleteTask for 'doot' source just updates
the DB — no external API call, no token dependency.

Migration path:
  POST /settings/import-from-todoist  — copies Todoist cache → native_tasks
  Then remove TODOIST_TOKEN from .env to disable Todoist

Changes:
- migration 020: native_tasks table
- store: GetNativeTasks, GetNativeTasksByDateRange, GetUndatedNativeTasks,
  CreateNativeTask, CompleteNativeTask, UncompleteNativeTask,
  UpdateNativeTask, ImportFromTodoist
- timeline: native tasks appear as source="doot" (teal)
- handleAtomToggle: "doot" case — no external API needed
- HandleWidgetComplete: method on Handler, handles "doot" natively
- HandleUnifiedAdd: "doot" source creates in native_tasks
- widget: "doot" tasks are completable, teal color indicator

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

1 files changed, 45 insertions, 0 deletions

diff --git a/internal/handlers/timeline_logic.go b/internal/handlers/timeline_logic.go
index 8430ee9..c9510bf 100644
--- a/internal/handlers/timeline_logic.go
+++ b/internal/handlers/timeline_logic.go
@@ -172,6 +172,51 @@ func BuildTimeline(ctx context.Context, s *store.Store, start, end time.Time) ([
 		}
 	}
 
+	// 6. Fetch native (doot-owned) tasks
+	nativeDated, err := s.GetNativeTasksByDateRange(start, end)
+	if err != nil {
+		log.Printf("Warning: failed to read native tasks: %v", err)
+	} else {
+		for _, task := range nativeDated {
+			if task.DueDate == nil {
+				continue
+			}
+			item := models.TimelineItem{
+				ID:           task.ID,
+				Type:         models.TimelineItemTypeTask,
+				Title:        task.Content,
+				Time:         *task.DueDate,
+				Description:  task.Description,
+				OriginalItem: task,
+				IsCompleted:  task.Completed,
+				Source:       "doot",
+			}
+			item.ComputeDaySection(now)
+			items = append(items, item)
+		}
+	}
+
+	nativeUndated, err := s.GetUndatedNativeTasks()
+	if err != nil {
+		log.Printf("Warning: failed to read undated native tasks: %v", err)
+	} else {
+		for _, task := range nativeUndated {
+			item := models.TimelineItem{
+				ID:           task.ID,
+				Type:         models.TimelineItemTypeTask,
+				Title:        task.Content,
+				Time:         now,
+				Description:  task.Description,
+				OriginalItem: task,
+				IsCompleted:  task.Completed,
+				Source:       "doot",
+				IsAllDay:     true,
+			}
+			item.ComputeDaySection(now)
+			items = append(items, item)
+		}
+	}
+
 	// Sort items by Time
 	sort.Slice(items, func(i, j int) bool {
 		return items[i].Time.Before(items[j].Time)