The desktop UI was still rendering the old JPG preview asset, so the empty
state, sidebar, and settings pages continued to show the legacy glow-backed
image even after the packaged app icon was corrected. This switches those UI
surfaces to a PNG generated from the current canonical app icon source so the
in-app preview matches the shipped icon treatment.
Constraint: The desktop UI still referenced a legacy JPG asset with the removed outer glow background
Constraint: There are unrelated staged changes in the worktree, so this commit must stay file-scoped
Rejected: Leave the UI on the JPG asset | keeps showing a stale icon treatment after the packaging fix
Rejected: Revert the packaged icon to match the old JPG | would reintroduce the original square-background problem
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: Keep desktop/public/app-icon.png in sync with desktop/src-tauri/app-icon.svg when the app icon changes
Tested: desktop bun run lint; desktop bun run test
Not-tested: Manual visual pass in the running desktop app after rebuilding the frontend bundle
