Fix CI build errors blocking v1.0.0 release #4797

Originally written by @ccantynz-alt on GitHub.
Imported from https://github.com/ccantynz-alt/voxlen/pull/4

Fixes the 6 TypeScript errors and the Xcode_15.4 iOS runner error that broke the first v1.0.0 workflow run.

What was red

• src/App.tsx — imported AdminPanel with no render case, called useHistoryStore without importing it
• src/components/dictation/DictationPanel.tsx — whole voiceCommands import block unused, referenced saveTranscripts and showWaveform that didn't exist in scope
• src/components/dictation/HistoryPanel.tsx — referenced saveTranscripts without importing it from the settings store
• .github/workflows/build.yml — hardcoded /Applications/Xcode_15.4.app which doesn't exist on macos-latest

What changed

• App.tsx: added useHistoryStore import, added admin case to renderView so the Sidebar's Admin button actually works
• DictationPanel: dropped the unused voiceCommands imports, subscribed to showWaveform from settings, cleaned stale deps in the toggle callback
• HistoryPanel: pulled saveTranscripts from settings store
• build.yml: removed the Xcode version pin, gated the iOS keyboard build on the xcodeproj existing, marked the iOS job continue-on-error so a missing iOS project never blocks the desktop release artifacts

Verified locally: npm run build (tsc + vite) passes clean.