style: light theme and hand-inked logo matching acampada26s.net

The previous pass kept the dark base and the red icons, which did not
read as the acampada. Now:

- Light theme: white page, black ink and borders, black buttons with a
  hard neon offset shadow, neon for focus and the active nav item;
  h1/h2 in Anton with the stepped neon shadow of the site headings.
- Nav, empty-state, spinner and pattern assets in black; platform icons
  keep their dark disc with a neon stroke.
- New mark: three dome tents wired from their doors into a switch with
  an antenna, drawn in the inked style of the acampada logo (curved
  poles, ball ends, hatching) over a neon offset copy. LogoMark renders
  it inline; visible product name is T-HUB.
- docs/brand: t-hub.svg and a lockup with the Anton wordmark converted
  to outlines so it renders without the font.
- Public submission page moved to the light palette.

Checked with headless Chromium screenshots (offline sample data) on
desktop and mobile.

apps/web/src/app/join/[token]/page.tsx

@@ -324,11 +324,11 @@ export default function JoinWorkspacePage({ params }: { params: { token: string
     <Card className="w-[520px] max-w-full p-6">
       <div className="mb-5 text-center">
         <img
-          src="/brand/hero.png"
-          alt="Tactical Media Broadcast Hub — arrows from a circle, warm red on black"
-          width={1024}
-          height={1024}
-          className="mx-auto mb-3 h-20 w-20 rounded-lg object-cover"
+          src="/brand/t-hub.svg"
+          alt="T-HUB: three tents wired to a switch with an antenna"
+          width={400}
+          height={400}
+          className="mx-auto mb-3 h-20 w-20"
         />
         <h1 className="text-xl font-semibold tracking-tight">Join {info.workspaceName}</h1>
         <p className="mt-1 text-2xs text-text-faint">