Task 3 - TypeScript Compiler Safety

[G-Jeffreys]

3.1 Set allowJs: false and migrate stray .js files to .ts or add JSDoc types.
3.2 Change target to "ES2022" to align with "moduleResolution": "bundler".
3.3 Tighten config with exactOptionalPropertyTypes and noPropertyAccessFromIndexSignature.
3.4 Restrict path aliases to "@/": ["src/"] for predictable IntelliSense.