Fix #946: Add standard iterator traits to CharPointer_UTF8 for compatibility with std algorithms

- Added value_type, pointer, reference, iterator_category, and difference_type typedefs
- Enables CharPointer_UTF8 to work with standard library algorithms like std::all_of
- Uses input_iterator_tag as the most appropriate category for UTF-8 character iteration
- Maintains full backward compatibility with existing code
- Tested with both GCC and Clang compilers

Author: killerdevildog

modules/juce_core/text/juce_CharPointer_UTF8.h

@@ -48,6 +48,13 @@ class CharPointer_UTF8  final
 public:
     using CharType = char;
 
+    // Standard iterator traits for compatibility with STL algorithms
+    using value_type = juce_wchar;
+    using pointer = juce_wchar*;
+    using reference = juce_wchar;  // Note: returns by value since this is a proxy iterator
+    using iterator_category = std::input_iterator_tag;
+    using difference_type = std::ptrdiff_t;
+
     explicit CharPointer_UTF8 (const CharType* rawPointer) noexcept
         : data (const_cast<CharType*> (rawPointer))
     {