fix(#1): Address code review findings

- Convert ApiResponse to discriminated union for type-safe error handling
- Add HealthStatus type with HealthState literal union
- Make BaseEntity fields readonly for immutability
- Add GlobalExceptionFilter with structured logging
- Add port validation with clear error messages in main.ts
- Improve parseDate to log warnings for invalid dates
- Add comprehensive Button tests (variants, onClick, disabled)
- Add slugify edge case tests (empty, special chars, numbers)
- Create ESLint configs for all packages
- Remove compiled JS files from src directories
- Convert .prettierrc.js to .prettierrc.json

Refs #1

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

packages/config/eslint/nestjs.js

@@ -4,9 +4,9 @@ export default [
   ...baseConfig,
   {
     rules: {
-      "@typescript-eslint/interface-name-prefix": "off",
       "@typescript-eslint/explicit-function-return-type": "off",
       "@typescript-eslint/explicit-module-boundary-types": "off",
+      "@typescript-eslint/no-extraneous-class": "off",
     },
   },
 ];