docs: Add FUTURE_UI_IDEAS.md blueprint

[DivyanshuChipa]

Creates a conceptual blueprint document for a future UI enhancement. The user requested to brainstorm a 'super app' style horizontal slide-out menu to replace the top bar in the Android ContactsScreen without making immediate code changes. This captures the design concept, animation styles, and planned icons (Settings, SMB Network, Intra Home) for later implementation.

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PR created automatically by Jules for task 10661622493270419977 started by @DivyanshuChipa

[google-labs-jules]

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