feat: externalize buttplug as separate nginx container

- Add Dockerfile.buttplug: builds Rust/WASM + TS, serves via nginx
- Add nginx.buttplug.conf: serves /dist and /wasm with correct MIME types
- Add .gitea/workflows/docker-build-buttplug.yml: path-filtered CI workflow
- Strip Rust toolchain and buttplug build from frontend Dockerfile
- Move buttplug to devDependencies (types only at build time)
- Remove vite-plugin-wasm from frontend (WASM now served by nginx)
- Add /buttplug proxy in vite.config (dev: localhost:8080)
- Add buttplug service to compose.yml
- Load buttplug dynamically in play page via runtime import
- Fix faq page: suppress no-unnecessary-state-wrap for reassigned SvelteSet

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

packages/frontend/src/routes/faq/+page.svelte

@@ -8,7 +8,8 @@
   import Meta from "$lib/components/meta/meta.svelte";
 
   let searchQuery = $state("");
-  let expandedItems = new SvelteSet<number>();
+  // eslint-disable-next-line svelte/no-unnecessary-state-wrap -- variable is reassigned, $state is required
+  let expandedItems = $state(new SvelteSet<number>());
 
   const faqCategories = [
     {