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.

cypress.config.ts

@@ -11,8 +11,16 @@ export default defineConfig({
   videosFolder: `${CYPRESS_BASE_DIR}/videos`,
 
   e2e: {
-    baseUrl: `http://localhost:${ViteConfig.server.port}/`,
+    baseUrl: `http://localhost:${getApplicationPort()}/`,
     specPattern: `${CYPRESS_BASE_DIR}/**/*.cy.{js,jsx,ts,tsx}`, // Default: cypress/e2e/**/*.cy.{js,jsx,ts,tsx}
     supportFile: `${CYPRESS_BASE_DIR}/support/e2e.ts`,
   },
 });
+
+function getApplicationPort(): number {
+  const port = ViteConfig.server?.port;
+  if (port === undefined) {
+    throw new Error('Unknown application port');
+  }
+  return port;
+}