docs: rename section titles in model and solution manuals

- Change 'Attributes and properties' to 'API Reference by Component'
- Update section titles in manual-model.md and manual-solution.md
- Remove temporary private.md file

Author: ocots

docs/src/api/private.md

@@ -17,7 +17,7 @@ After covering these core functionalities, we'll delve into the **structure of a
 
 * [Main functionalities](@ref manual-model-main-functionalities)
 * [Model struct](@ref manual-model-struct)
-* [Attributes and properties](@ref manual-model-attributes)
+* [API Reference by Component](@ref manual-model-api)
 
 ---
 

docs/src/manual-model.md

@@ -13,7 +13,7 @@ After covering these core functionalities, we'll delve into the **structure of a
 
 * [Main functionalities](@ref manual-solution-main-functionalities)
 * [Solution struct](@ref manual-solution-struct)
-* [Attributes and properties](@ref manual-solution-attributes)
+* [API Reference by Component](@ref manual-solution-api)
 
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