feat(cli): add ascii art banner on server startup

[arabold]

Summary

Adds a stylish ASCII art "Grounded Docs" banner that displays on HTTP server startup.

• Gray/white gradient: Top line in gray, bottom line in bright white for a modern look
• Configurable: --logo / --no-logo CLI flag (default: show logo)
• Non-intrusive: Only shows for HTTP server startup, not stdio mode
• Docker-optimized: Only worker shows banner in docker-compose (mcp/web use --no-logo)

Preview

  █▀▀ █▀█ █▀█ █ █ █▄ █ █▀▄ █▀▀ █▀▄   █▀▄ █▀█ █▀▀ █▀▀   (gray)
  █▄█ █▀▄ █▄█ █▄█ █ ▀█ █▄▀ ██▄ █▄▀   █▄▀ █▄█ █▄▄ ▄▄█   (bright white)

🚀 Worker available at http://localhost:8080

Files Changed

• src/utils/banner.ts - New banner utility
• src/cli/index.ts - Global --logo option
• src/app/AppServerConfig.ts - showLogo config property
• src/cli/utils.ts - Updated createAppServerConfig()
• src/cli/commands/*.ts - Pass showLogo through
• src/app/AppServer.ts - Conditional banner display
• docker-compose.yml - --no-logo for mcp/web services