feat: use natural sort in file browser (#722)

## Summary

* **What is the goal of this PR?** (e.g., Implements the new feature for
file uploading.)

Implement natural sort (e.g. "file1.txt, file2.txt, file10.txt" instead
of "file1.txt, file10.txt, file2.txt") for files in the
MyLibraryActivity menu

* **What changes are included?**

Modifies the `sortFileList` function under
`src/activities/home/MyLibraryActivity.cpp` to use natural sort as
opposed to lexicographical sort

## Additional Context

I wasn't entirely sure whether or not i should make this a configurable
option, but most file browsers and directory listing tools have this set
as an immutable default, so I opted against it.

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
  specific areas to focus on).

---

### 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? _**NO**_

src/activities/home/MyLibraryActivity.cpp

@@ -16,11 +16,53 @@ constexpr unsigned long GO_HOME_MS = 1000;
 
 void sortFileList(std::vector<std::string>& strs) {
   std::sort(begin(strs), end(strs), [](const std::string& str1, const std::string& str2) {
-    if (str1.back() == '/' && str2.back() != '/') return true;
-    if (str1.back() != '/' && str2.back() == '/') return false;
-    return lexicographical_compare(
-        begin(str1), end(str1), begin(str2), end(str2),
-        [](const char& char1, const char& char2) { return tolower(char1) < tolower(char2); });
+    // Directories first
+    bool isDir1 = str1.back() == '/';
+    bool isDir2 = str2.back() == '/';
+    if (isDir1 != isDir2) return isDir1;
+
+    // Start naive natural sort
+    const char* s1 = str1.c_str();
+    const char* s2 = str2.c_str();
+
+    // Iterate while both strings have characters
+    while (*s1 && *s2) {
+      // Check if both are at the start of a number
+      if (isdigit(*s1) && isdigit(*s2)) {
+        // Skip leading zeros and track them
+        const char* start1 = s1;
+        const char* start2 = s2;
+        while (*s1 == '0') s1++;
+        while (*s2 == '0') s2++;
+
+        // Count digits to compare lengths first
+        int len1 = 0, len2 = 0;
+        while (isdigit(s1[len1])) len1++;
+        while (isdigit(s2[len2])) len2++;
+
+        // Different length so return smaller integer value
+        if (len1 != len2) return len1 < len2;
+
+        // Same length so compare digit by digit
+        for (int i = 0; i < len1; i++) {
+          if (s1[i] != s2[i]) return s1[i] < s2[i];
+        }
+
+        // Numbers equal so advance pointers
+        s1 += len1;
+        s2 += len2;
+      } else {
+        // Regular case-insensitive character comparison
+        char c1 = tolower(*s1);
+        char c2 = tolower(*s2);
+        if (c1 != c2) return c1 < c2;
+        s1++;
+        s2++;
+      }
+    }
+
+    // One string is prefix of other
+    return *s1 == '\0' && *s2 != '\0';
   });
 }