fix: move esbuild platform binaries to optionalDependencies

[sanskarOH]

What changed

Moved @esbuild/darwin-arm64 and @esbuild/darwin-x64 from dependencies to optionalDependencies in package.json (and regenerated package-lock.json to match).

Why

Fresh npm install fails on any single-arch Mac with:

npm error code EBADPLATFORM
npm error notsup Unsupported platform for @esbuild/darwin-x64@0.19.12: wanted {"os":"darwin","cpu":"x64"} (current:  {"os":"darwin","cpu":"arm64"})

npm treats platform-restricted packages as hard requirements when listed under regular dependencies, so it aborts install rather than skipping the incompatible binary. optionalDependencies is npm's correct mechanism for this — it installs the compatible binary and silently skips the other, which also aligns with the existing scripts/ensure-cross-arch-esbuild.mjs postinstall step that fetches the missing cross-arch binary separately.

Compatibility impact

None expected. Both binaries are still declared with pinned versions; only the dependency type changed. Cross-arch packaging (electron-builder producing both Intel and Apple Silicon builds) is unaffected since ensure-cross-arch-esbuild.mjs already handles fetching the missing binary post-install.

How I tested

• npm install succeeds cleanly on an arm64 Mac (previously failed with EBADPLATFORM)
• npm run build completes without errors (main, renderer, and native builds all pass)
• npm run dev launches the app successfully with all core features (clipboard, snippets, commands) loading correctly
• Verified node_modules/@esbuild/ contains the arm64 binary after install, and confirmed lockfile correctly reflects optionalDependencies