fix(splash): Keep the wordmark still until the splash fades

The splash named Inter, but the font faces and antialiasing came with the app CSS,
which the dev server injects only once the bundle runs: the wordmark switched from
the system font to Inter, moving up and changing weight, just before the fade. The
font faces are now linked from index.html and the splash sets its own smoothing.
The splash also stays on one compositing layer, so the fade-out doesn't re-snap
the centred text.

src/styles/fonts.css

@@ -0,0 +1,4 @@
+/* Linked from index.html rather than imported by global.css, so the faces are known before the
+   splash first paints: the dev server injects the app CSS only once the bundle runs. */
+@import "@fontsource-variable/inter";
+@import "@fontsource-variable/jetbrains-mono";