[FEAT] Customizable footer icon links in Appearance Settings (#694)

* WIP custom footer icons

* UI for updating footer icons complete and backend to save/modify

* add backend for unprotected footer fetch

* break out footer into separate component and render footer items using a cache for 1 hour

* wip review

* refactor & cleanup

* Optimize footer form component
Optimize caching for footer icons
Add validation on SystemSetting upserts
Normalize fallback items for footer_data

* Adjust max icons to 3

* fix success message on remove

* fix success message on remove

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Co-authored-by: timothycarambat <rambat1010@gmail.com>