feat: add auto-login for dev mode and fix log box formatting (#567)

* feat: add auto-login for dev mode and fix log box formatting

Add AUTOMAKER_AUTO_LOGIN environment variable that, when set to 'true',
automatically creates a session for web mode users without requiring
them to enter the API key. Useful for development environments.

Also fix formatting issues in console log boxes:
- API Key box: add right border, show auto-login status and tips
- Claude auth warning: add separator line, fix emoji spacing
- Server info box: use consistent 71-char width, proper padding
- Port conflict error: use same width, proper dynamic padding

Environment variables:
- AUTOMAKER_AUTO_LOGIN=true: Skip login prompt, auto-create session
- AUTOMAKER_API_KEY: Use a fixed API key (existing)
- AUTOMAKER_HIDE_API_KEY=true: Hide the API key banner (existing)

* fix: add production safeguard to auto-login and extract log box constant

- Add NODE_ENV !== 'production' check to prevent auto-login in production
- Extract magic number 67 to BOX_CONTENT_WIDTH constant in auth.ts and index.ts
- Document AUTOMAKER_AUTO_LOGIN env var in CLAUDE.md and README.md

CLAUDE.md

@@ -172,4 +172,5 @@ Use `resolveModelString()` from `@automaker/model-resolver` to convert model ali
 - `DATA_DIR` - Data storage directory (default: ./data)
 - `ALLOWED_ROOT_DIRECTORY` - Restrict file operations to specific directory
 - `AUTOMAKER_MOCK_AGENT=true` - Enable mock agent mode for CI testing
+- `AUTOMAKER_AUTO_LOGIN=true` - Skip login prompt in development (disabled when NODE_ENV=production)
 - `VITE_HOSTNAME` - Hostname for frontend API URLs (default: localhost)