Built-in Opus codec for browsers without one; cameras on by default with per-person hide

- libopus in WebAssembly takes over voice where WebCodecs audio is missing
  (Firefox on Android); tested for tone, timing and bitrate, and in a browser
  forced onto it
- Cameras in the channel show by themselves once the IP note was confirmed;
  a person's camera can be hidden from the right-click menu, all of them with
  one button; an enlarged camera leaves its tile
- CSP allows wasm-unsafe-eval for the codec

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -90,6 +90,7 @@
     }
   },
   "devDependencies": {
+    "@evan/opus": "^1.0.3",
     "@sveltejs/vite-plugin-svelte": "^7.3.1",
     "@tsconfig/svelte": "^5.0.8",
     "@types/node": "^26.6.3",