Allow setting an animation source by asset path

[Gopmyc]

Description

Adds a const std::string& overload of CSkinnedMeshRenderer::SetAnimationSourceModel that
resolves the path through ModelManager, and binds it alongside the existing Model* form.
Scripts can now assign an animation source, which was previously impossible: Lua has no way to
obtain a Model*.

Resolution lives in the component, next to the existing setter, so the binding stays a plain
sol::overload of two sol::resolve entries, the same shape already used for SetAnimation.
An empty path clears the source; an unresolvable one is logged and leaves the current source
untouched.

Related Issue(s)

Fixes #835

Review Guidance

Behaviour of the existing Model* overload is unchanged; no current call site passes a literal
nullptr, so the added overload introduces no ambiguity. CMaterialRenderer already resolves its
assets through ServiceLocator, so the component-side dependency on ModelManager is not new.

Screenshots/GIFs

N/A

AI Usage Disclosure

N/A

Checklist

• My code follows the project's code style guidelines
• When applicable, I have commented my code, particularly in hard-to-understand areas
• When applicable, I have updated the documentation accordingly
• My changes don't generate new warnings or errors
• I have reviewed and take responsibility for all code in this PR (including any AI-assisted contributions)

[adriengivry]

See #835 (comment)

Happy to discuss if needed