♻️ refactor: split into testable modules, add test suite

package.json

@@ -13,6 +13,7 @@
     "winston": "3.19.0"
   },
   "devDependencies": {
+    "@types/bun": "^1.3.14",
     "@types/node": "^26.0.1",
     "@types/validator": "^13.15.10",
     "prettier": "^3.9.4",
@@ -22,7 +23,8 @@
     "typecheck": "tsc --noEmit",
     "format": "prettier --check .",
     "format:fix": "prettier --write .",
-    "check": "bun run typecheck && bun run format",
+    "check": "bun run typecheck && bun run format && bun test",
+    "test": "bun test",
     "dev": "bun --watch src/index.ts",
     "start": "bun src/index.ts",
     "build": "bun run typecheck",