feat: implement configuration management system

- Add comprehensive TypeScript interfaces for all config types
- Implement ConfigManager singleton class with layered loading
- Support for default, environment-specific, and environment variable configs
- Add example .env file for sensitive configuration

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

config/development.json

@@ -0,0 +1,7 @@
+{
+  "logLevel": "debug",
+  "browser": {
+    "headless": false,
+    "slowMo": 100
+  }
+}