Fix .link buttons collapsing onto one line at wide --bl-max-width

button.link overrode width back to auto (from the general button
rule's width: 100%) but never set display: block, so it stayed at the
<button> default of inline-block. At narrow widths (the default
380px card) two adjacent .link buttons happened to wrap onto separate
lines simply because they didn't fit side by side, masking the bug.
At --bl-max-width: none in a wide host container (found integrating
BitLogin into BitUnlock's /connect page), "Import an existing Nostr
key" and "Forgot password? Recover with phrase" rendered running into
each other on the same line.

packages/widget/src/styles.ts

@@ -195,6 +195,7 @@ button.primary:disabled { opacity: 0.55; cursor: default; }
 button.secondary { background: transparent; color: var(--bl-fg); border: 1px solid var(--bl-border); }
 button.secondary:hover { background: var(--bl-input-bg); }
 button.link {
+  display: block;
   background: none;
   color: var(--bl-accent);
   width: auto;