Review comments

Co-authored-by: Copilot <copilot@github.com>

src/FontInstaller.h

@@ -19,6 +19,8 @@ class FontInstaller {
 
   explicit FontInstaller(SdCardFontRegistry& registry);
 
+  static constexpr size_t MAX_FAMILY_NAME_LEN = 64;
+
   /// Validate a family name: alphanumeric + hyphen + underscore only, no path traversal.
   static bool isValidFamilyName(const char* name);