Add feature toggles system with settings UI (#74)

- Add feature_toggles table (migration 012)
- Add source_config table for future source selection (migration 013)
- Create settings page at /settings with:
  - Feature toggle management (enable/disable/create/delete)
  - Data source configuration (sync and toggle boards/calendars)
- Add store methods for feature toggles and source config
- Add GetCalendarList and GetTaskLists to Google API clients
- Document feature toggle workflow in DESIGN.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

3 files changed, 40 insertions, 0 deletions

diff --git a/internal/api/google_calendar.go b/internal/api/google_calendar.go
index d2d4355..68d423b 100644
--- a/internal/api/google_calendar.go
+++ b/internal/api/google_calendar.go
@@ -175,3 +175,24 @@ func (c *GoogleCalendarClient) GetEventsByDateRange(ctx context.Context, start,
 
 	return deduplicateEvents(allEvents), nil
 }
+
+// GetCalendarList returns all calendars accessible to the user
+func (c *GoogleCalendarClient) GetCalendarList(ctx context.Context) ([]models.CalendarInfo, error) {
+	list, err := c.srv.CalendarList.List().Do()
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch calendar list: %w", err)
+	}
+
+	var calendars []models.CalendarInfo
+	for _, item := range list.Items {
+		name := item.Summary
+		if name == "" {
+			name = item.Id
+		}
+		calendars = append(calendars, models.CalendarInfo{
+			ID:   item.Id,
+			Name: name,
+		})
+	}
+	return calendars, nil
+}
diff --git a/internal/api/google_tasks.go b/internal/api/google_tasks.go
index 0b4d7c2..77a00ed 100644
--- a/internal/api/google_tasks.go
+++ b/internal/api/google_tasks.go
@@ -171,3 +171,20 @@ func (c *GoogleTasksClient) UncompleteTask(ctx context.Context, listID, taskID s
 	}
 	return nil
 }
+
+// GetTaskLists returns all task lists accessible to the user
+func (c *GoogleTasksClient) GetTaskLists(ctx context.Context) ([]models.TaskListInfo, error) {
+	list, err := c.srv.Tasklists.List().Context(ctx).Do()
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch task lists: %v", err)
+	}
+
+	var lists []models.TaskListInfo
+	for _, item := range list.Items {
+		lists = append(lists, models.TaskListInfo{
+			ID:   item.Id,
+			Name: item.Title,
+		})
+	}
+	return lists, nil
+}
diff --git a/internal/api/interfaces.go b/internal/api/interfaces.go
index aa351ab..1c102a7 100644
--- a/internal/api/interfaces.go
+++ b/internal/api/interfaces.go
@@ -40,6 +40,7 @@ type PlanToEatAPI interface {
 type GoogleCalendarAPI interface {
 	GetUpcomingEvents(ctx context.Context, maxResults int) ([]models.CalendarEvent, error)
 	GetEventsByDateRange(ctx context.Context, start, end time.Time) ([]models.CalendarEvent, error)
+	GetCalendarList(ctx context.Context) ([]models.CalendarInfo, error)
 }
 
 // GoogleTasksAPI defines the interface for Google Tasks operations
@@ -48,6 +49,7 @@ type GoogleTasksAPI interface {
 	GetTasksByDateRange(ctx context.Context, start, end time.Time) ([]models.GoogleTask, error)
 	CompleteTask(ctx context.Context, listID, taskID string) error
 	UncompleteTask(ctx context.Context, listID, taskID string) error
+	GetTaskLists(ctx context.Context) ([]models.TaskListInfo, error)
 }
 
 // Ensure concrete types implement interfaces