Allow frequency override in Playlist, Folder fixes (#1194)

* Allow frequency to be changed per-entry

* Folder fixes, use TX freq

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Co-authored-by: kallanreed <kallanreed@noreply.github.com>

firmware/common/optional.hpp

@@ -34,6 +34,17 @@ class Optional {
     constexpr Optional(T&& value)
         : value_{std::move(value)}, valid_{true} {}
 
+    constexpr Optional& operator=(const T& value) {
+        value_ = value;
+        valid_ = true;
+        return *this;
+    }
+    constexpr Optional& operator=(T&& value) {
+        value_ = std::move(value);
+        valid_ = true;
+        return *this;
+    }
+
     bool is_valid() const { return valid_; }
     operator bool() const { return valid_; }