feat: improve unified config system and build process

- Enhance unified config environment variable loading with better precedence
- Add environment-aware validation (production validation only when NODE_ENV=production)
- Add environment-specific build commands (build:dev, build:prod, build:staging)
- Improve configuration debugging with cleaner logging
- Remove unnecessary development warnings
- Provides more flexible and maintainable configuration system

package.json

@@ -6,7 +6,10 @@
   "scripts": {
     "predev": "./scripts/process-html.sh",
     "dev": "vite",
-    "build": "vite build",
+    "build": "NODE_ENV=development vite build",
+    "build:prod": "NODE_ENV=production vite build",
+    "build:dev": "NODE_ENV=development vite build",
+    "build:staging": "NODE_ENV=staging vite build",
     "preview": "vite preview",
     "lint": "eslint . --ext .ts,.tsx",
     "lint:fix": "eslint . --ext .ts,.tsx --fix",