feat(web): theme tokens, self-hosted Inter, HTML entry

DESIGN.md tokens as CSS custom properties. Inter (OFL) is vendored so the
app makes no third-party font requests.

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

apps/web/index.html

@@ -1 +1,15 @@
-<!doctype html><title>STTracker</title><div id="root">STTracker is starting…</div>
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <meta name="color-scheme" content="dark" />
+    <meta name="theme-color" content="#17152b" />
+    <title>STTracker</title>
+    <link rel="stylesheet" href="./src/theme.css" />
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="./src/main.tsx"></script>
+  </body>
+</html>