Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

src/presentation/components/Shared/Icon/UseSvgLoader.ts

@@ -62,7 +62,7 @@ const RawSvgLoaders = import.meta.glob('@/presentation/assets/icons/**/*.svg', {
 });
 
 function modifySvg(svgSource: string): string {
-  const parser = new window.DOMParser();
+  const parser = new globalThis.window.DOMParser();
   const doc = parser.parseFromString(svgSource, 'image/svg+xml');
   let svgRoot = doc.documentElement;
   svgRoot = removeSvgComments(svgRoot);