* app: harden update flows
This hardens the windows update flows and adds a new opt-in and CI triggered unit test to verify Mac/Windows updates with verification.
* test: harden unit tests for OLLAMA_MODELS being set
* app: harden updater
* app: add code for macOS and Windows apps under 'app'
* app: add readme
* app: windows and linux only for now
* ci: fix ui CI validation
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Co-authored-by: jmorganca <jmorganca@gmail.com>
