Fix Windows build error: wrap std::max in parentheses to avoid macro conflict

- On Windows, max/min are often defined as macros by windows.h
- This causes compilation errors with std::max/std::min
- Solution: use (std::max) to prevent macro expansion
- Fixes CI build error: error C2589: '(': illegal token on right side of '::'

Fixes: error in coalesce_ranges function on line 5376

Author: yhirose

httplib.h

@@ -5373,7 +5373,7 @@ inline void coalesce_ranges(Ranges &ranges, size_t content_length) {
       if (first_pos <= prev.second + 1 &&
           !(first_pos == prev.first && last_pos == prev.second)) {
         // Extend the previous range
-        prev.second = std::max(prev.second, last_pos);
+        prev.second = (std::max)(prev.second, last_pos);
         continue;
       }
     }