Refactor DI for simplicity and type safety

This commit improves the dependency injection mechanism by introducing a
custom `injectKey` function.

Key improvements are:

- Enforced type consistency during dependency registration and
  instantiation.
- Simplified injection process, abstracting away the complexity with a
  uniform API, regardless of the dependency's lifetime.
- Eliminated the possibility of `undefined` returns during dependency
  injection, promoting fail-fast behavior.
- Removed the necessity for type casting to `symbol` for injection keys
  in unit tests by using existing types.
- Consalidated imports, combining keys and injection functions in one
  `import` statement.

tests/unit/presentation/components/Code/CodeButtons/CodeCopyButton.spec.ts

@@ -39,12 +39,12 @@ function mountComponent(options?: {
   return shallowMount(CodeCopyButton, {
     global: {
       provide: {
-        [InjectionKeys.useClipboard as symbol]: () => (
+        [InjectionKeys.useClipboard.key]: () => (
           options?.clipboard
             ? new UseClipboardStub(options.clipboard)
             : new UseClipboardStub()
         ).get(),
-        [InjectionKeys.useCurrentCode as symbol]: () => (
+        [InjectionKeys.useCurrentCode.key]: () => (
           options.currentCode === undefined
             ? new UseCurrentCodeStub()
             : new UseCurrentCodeStub().withCurrentCode(options.currentCode)