Preserve case in !rt token input

The !rt token is case-sensitive and often contains capitals, but the
input CSS lowercased typed characters visually (misleading) and the
placeholder "abcd" implied lowercase-only. Server-side validation and
loginWithToken() already preserved case — only the UI was wrong.

- Drop text-transform: lowercase from the input
- Placeholder abcd -> aB3d

src/lib/ui/components/TokenModal.svelte

@@ -63,7 +63,7 @@
                     maxlength="4"
                     minlength="4"
                     pattern="[a-zA-Z0-9]{'{'}4{'}'}"
-                    placeholder="abcd"
+                    placeholder="aB3d"
                     bind:value
                     disabled={submitting}
                     aria-label="4-character !rt token"
@@ -128,7 +128,6 @@
         font-family: 'JetBrains Mono', ui-monospace, monospace;
         letter-spacing: 8px;
         text-align: center;
-        text-transform: lowercase;
     }
     button {
         background: #ff3030;