feat: add semantic-release for automated versioning and help dialog

- Set up semantic-release with zero-touch CI pipeline on push to main
- Add version sync script to keep all package.json files and APP_VERSION
  constant in sync automatically
- Consolidate Docker publishing into single tag-triggered workflow that
  pushes to both Docker Hub and ghcr.io with semver tags
- Add help dialog with keyboard shortcuts, getting started guide, and
  resource links
- Sync all versions to 0.2.1 to match Docker Hub latest

apps/api/src/routes/tools/remove-background.ts

@@ -55,7 +55,7 @@ export function registerRemoveBackground(app: FastifyInstance) {
         const resultBuffer = await removeBackground(
           fileBuffer,
           join(workspacePath, "output"),
-          { model: settings.model },
+          { model: settings.model, backgroundColor: settings.backgroundColor },
         );
 
         // Save output