perf: Skip constructing unnecessary std::string (#932)

## Summary

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

Skip constructing a `std::string` just to get the underlying `c_str()`
buffer, when a string literal gives the same end result.

---

### 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**_

lib/Epub/Epub/blocks/TextBlock.cpp

@@ -30,7 +30,7 @@ void TextBlock::render(const GfxRenderer& renderer, const int fontId, const int
       if (w.size() >= 3 && static_cast<uint8_t>(w[0]) == 0xE2 && static_cast<uint8_t>(w[1]) == 0x80 &&
           static_cast<uint8_t>(w[2]) == 0x83) {
         const char* visiblePtr = w.c_str() + 3;
-        const int prefixWidth = renderer.getTextAdvanceX(fontId, std::string("\xe2\x80\x83").c_str());
+        const int prefixWidth = renderer.getTextAdvanceX(fontId, "\xe2\x80\x83");
         const int visibleWidth = renderer.getTextWidth(fontId, visiblePtr, currentStyle);
         startX = wordX + prefixWidth;
         underlineWidth = visibleWidth;