refactor(console): remove modern renderer, keep VT220 only

Remove the Rich-based textual renderer and all --mode modern references.
The console now runs exclusively in VT220 curses mode (green on black).
No external dependencies required.

Removed: console/renderers/textual_renderer.py, --mode flag, DEFAULT_MODE
Updated: main.py, config.py, README.md, console/README.md

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

console/config.py

@@ -19,7 +19,6 @@ NHTSA_API_URL = "https://vpic.nhtsa.dot.gov/api/vehicles/DecodeVin"
 VIN_CACHE_DAYS = 30
 
 # Display defaults
-DEFAULT_MODE = "vt220"
 PAGE_SIZE = 15
 
 # VT220 color pairs: (foreground, background)