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.

tests/unit/presentation/components/Shared/Hooks/Clipboard/BrowserClipboard.spec.ts

@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest';
 import { BrowserClipboard, NavigatorClipboard } from '@/presentation/components/Shared/Hooks/Clipboard/BrowserClipboard';
 import { StubWithObservableMethodCalls } from '@tests/unit/shared/Stubs/StubWithObservableMethodCalls';
 import { expectThrowsAsync } from '@tests/shared/Assertions/ExpectThrowsAsync';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
 
 describe('BrowserClipboard', () => {
   describe('writeText', () => {
@@ -16,7 +17,7 @@ describe('BrowserClipboard', () => {
       const calls = navigatorClipboard.callHistory;
       expect(calls).to.have.lengthOf(1);
       const call = calls.find((c) => c.methodName === 'writeText');
-      expect(call).toBeDefined();
+      expectExists(call);
       const [actualText] = call.args;
       expect(actualText).to.equal(expectedText);
     });