fix: move Linux-only native deps to optionalDependencies

`@remotion/compositor-linux-x64-gnu` and `@rspack/binding-linux-x64-gnu`
are Linux x64 binaries that cause npm install to fail on macOS (arm64)
with EBADPLATFORM. Moving them to optionalDependencies allows npm to
skip them gracefully on unsupported platforms.

Fixes #32

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -51,8 +51,6 @@
     "@fastify/compress": "^8.3.1",
     "@fastify/cookie": "^11.0.2",
     "@fastify/static": "^8.0.0",
-    "@remotion/compositor-linux-x64-gnu": "^4.0.432",
-    "@rspack/binding-linux-x64-gnu": "^1.7.7",
     "chalk": "^5.3.0",
     "chokidar": "^3.6.0",
     "commander": "^12.1.0",
@@ -93,6 +91,10 @@
     "typescript-eslint": "^8.0.0",
     "vitest": "^4.0.18"
   },
+  "optionalDependencies": {
+    "@remotion/compositor-linux-x64-gnu": "^4.0.432",
+    "@rspack/binding-linux-x64-gnu": "^1.7.7"
+  },
   "engines": {
     "node": ">=18.0.0"
   },