Enhance Graphviz dot output with status-based fill colors:
- open: white background (default)
- in_progress: light yellow background
- blocked: light coral background
- closed: light gray background with dimmed text
Node labels show: ID, type, priority, title, and status.
Priority is visible in the label (e.g., [bug P0]) but not color-coded
to keep the visualization clean and focused on status.