fix: support legacy XTC file headers where pageTableOffset=48 (#1816)

## Summary

**What is the goal of this PR?**

Restore compatibility with older XTC files that use the legacy 48-byte
header layout, so they open correctly instead of failing
header/page-table validation.

**What changes are included?**

- Updates the XTC parser to accept legacy files where pageTableOffset
starts at 0x30 instead of the newer full header size.
- Avoids treating legacy header bytes as a valid chapterOffset, so older
files are not misclassified as having chapters.
- Switches XTC file size and seek operations to 64-bit-safe wrapper
calls in HalStorage, which matches the XTC format’s 64-bit offset fields
and keeps page/chapter lookups from narrowing offsets.
- Keeps the existing bounds checks and improves related logging when XTC
page loads fail.

## Additional Context

- This is a narrow compatibility fix for XTC handling. The functional
change is in the XTC parser; the HalStorage changes are supporting
wrapper methods needed by that parser update.
- Risk should be low outside XTC reading, since the HAL changes only
expose existing underlying file APIs rather than changing storage
behavior.

---

### AI Usage

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helps set the right context for reviewers.

Did you use AI tools to help write this code? **YES**

src/activities/reader/XtcReaderActivity.cpp

@@ -179,7 +179,8 @@ void XtcReaderActivity::renderPage() {
   // Load page data
   size_t bytesRead = xtc->loadPage(currentPage, pageBuffer, pageBufferSize);
   if (bytesRead == 0) {
-    LOG_ERR("XTR", "Failed to load page %lu", currentPage);
+    LOG_ERR("XTR", "Failed to load page %lu: bufferSize=%lu bitDepth=%u error=%s", currentPage, pageBufferSize,
+            bitDepth, xtc::errorToString(xtc->getLastError()));
     free(pageBuffer);
     renderer.clearScreen();
     renderer.drawCenteredText(UI_12_FONT_ID, 300, tr(STR_PAGE_LOAD_ERROR), true, EpdFontFamily::BOLD);