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>

apps/web/package.json

@@ -6,8 +6,8 @@
     "build": "next build",
     "dev": "next dev --turbopack --port 3000",
     "start": "next start",
-    "lint": "next lint",
-    "lint:fix": "next lint --fix",
+    "lint": "eslint \"src/**/*.{ts,tsx}\"",
+    "lint:fix": "eslint \"src/**/*.{ts,tsx}\" --fix",
     "typecheck": "tsc --noEmit",
     "clean": "rm -rf .next",
     "test": "vitest run",