feat(frontend): bundle the icons so the app works offline

Every <wa-icon> was fetched from ka-f.fontawesome.com at runtime —
confirmed from `performance.getEntriesByType('resource')`, 36 requests
— so offline the app had no icons at all. `setBasePath()` does not
affect the icon resolver; only the component autoloader reads it.
Overriding Web Awesome's `default` icon library fixes all 165 call
sites without changing one of them. Cross-origin requests at startup:
22 -> 0.

Three things about it are load-bearing. The set is Font Awesome Free
(CC BY 4.0, vendored with its licence by `scripts/fetch-icons.mjs`)
because the kit CDN serves Pro, which cannot be redistributed. The
names are a committed list rather than anything derived, because
twenty call sites compute their icon name from state and no static
pass can enumerate them. And a name that is not bundled is reported at
runtime to `window.__yjIconMisses` and drawn as a fallback, since a
missing icon used to be impossible — the CDN having had everything.

frontend/src/assets/icons/fa/solid/volume-low.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! Font Awesome Free 7.3.1 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2026 Fonticons, Inc. --><path fill="currentColor" d="M48 352l48 0 134.1 119.2c6.4 5.7 14.6 8.8 23.1 8.8 19.2 0 34.8-15.6 34.8-34.8l0-378.4c0-19.2-15.6-34.8-34.8-34.8-8.5 0-16.7 3.1-23.1 8.8L96 160 48 160c-26.5 0-48 21.5-48 48l0 96c0 26.5 21.5 48 48 48zM380.6 181.5c-10.3-8.4-25.4-6.8-33.8 3.5s-6.8 25.4 3.5 33.8C361.1 227.6 368 241 368 256s-6.9 28.4-17.7 37.3c-10.3 8.4-11.8 23.5-3.5 33.8s23.5 11.8 33.8 3.5C402.1 312.9 416 286.1 416 256s-13.9-56.9-35.5-74.5z"/></svg>