chore: remove remotion and @remotion/player from dependencies

- Removed 'remotion' and '@remotion/player' from package.json
- Deleted Root.tsx (SSR composition registry, no longer needed for frontend)
- Updated build scripts to skip remotion:bundle step
- Kept @remotion/bundler and @remotion/renderer for server-side (Phase 4)
- Verified: electron-vite build passes cleanly

package-lock.json

@@ -12,7 +12,6 @@
         "@dnd-kit/utilities": "^3.2.2",
         "@google/genai": "^2.4.0",
         "@remotion/bundler": "^4.0.468",
-        "@remotion/player": "^4.0.468",
         "@remotion/renderer": "^4.0.468",
         "@tailwindcss/vite": "^4.1.14",
         "@vitejs/plugin-react": "^5.0.4",
@@ -27,7 +26,6 @@
         "papaparse": "^5.5.3",
         "react": "^19.0.1",
         "react-dom": "^19.0.1",
-        "remotion": "^4.0.468",
         "vite": "^6.2.3"
       },
       "devDependencies": {