Rename Feed.Status to Feed.FeedHealth

Clearer terminology: feed_health tracks whether a feed has been
verified and is working, separate from publish_status which tracks
publishing approval.

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

models.go

@@ -52,7 +52,7 @@ type Feed struct {
 	LastModified string `json:"last_modified,omitempty"`
 
 	// Health tracking
-	Status      string    `json:"status"` // "pass", "hold", "skip"
+	FeedHealth  string    `json:"feed_health"` // "pass", "hold", "skip", "dead"
 	LastError   string    `json:"last_error,omitempty"`
 	LastErrorAt time.Time `json:"last_error_at,omitempty"`