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/pen.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><!--! 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="M352.9 21.2L308 66.1 445.9 204 490.8 159.1C504.4 145.6 512 127.2 512 108s-7.6-37.6-21.2-51.1L455.1 21.2C441.6 7.6 423.2 0 404 0s-37.6 7.6-51.1 21.2zM274.1 100L58.9 315.1c-10.7 10.7-18.5 24.1-22.6 38.7L.9 481.6c-2.3 8.3 0 17.3 6.2 23.4s15.1 8.5 23.4 6.2l127.8-35.5c14.6-4.1 27.9-11.8 38.7-22.6L412 237.9 274.1 100z"/></svg>