fix: make file system operations thread-safe (HalFile) (#1212)

## Summary

Fix https://github.com/crosspoint-reader/crosspoint-reader/issues/1137

Introducing `HalFile`, a thin wrapper around `FsFile` that uses a global
mutex to protect file operations.

To test this PR, place the code below somewhere in the code base (I
placed it in `onGoToRecentBooks`)

```cpp
static auto testTask = [](void* param) {
  for (int i = 0; i < 10; i++) {
    String json = Storage.readFile("/.crosspoint/settings.json");
    LOG_DBG("TEST_TASK", "Read settings.json, bytes read: %u", json.length());
  }
  vTaskDelete(nullptr);
};
xTaskCreate(testTask, "test0", 8192, nullptr, 1, nullptr);
xTaskCreate(testTask, "test1", 8192, nullptr, 1, nullptr);
xTaskCreate(testTask, "test2", 8192, nullptr, 1, nullptr);
xTaskCreate(testTask, "test3", 8192, nullptr, 1, nullptr);
delay(1000);
```

It will reliably lead to crash on `master`, but will function correctly
with this PR.

A macro renaming trick is used to avoid changing too many downstream
code files.

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? **PARTIALLY**, only to
help with tedious copy-paste tasks

---------

Co-authored-by: Zach Nelson <zach@zdnelson.com>

src/CrossPointSettings.h

@@ -1,10 +1,9 @@
 #pragma once
+#include <HalStorage.h>
+
 #include <cstdint>
 #include <iosfwd>
 
-// Forward declarations
-class FsFile;
-
 class CrossPointSettings {
  private:
   // Private constructor for singleton