fix(web): make anchor-styled buttons readable

The .btn class sets color:var(--accent-fg), but the generic a{} and
a:visited{} rules outrank it on <a> elements, so anchor buttons (the
landing "Get Started" CTA, "Connect YouTube") rendered their label
accent-on-accent — invisible. Add a.btn / a.btn:visited to restore the
button foreground.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/web/view.go

@@ -479,6 +479,10 @@ main { max-width: 60rem; margin: 0 auto; padding: var(--s4) var(--s3); }
 .filters input { font: inherit; padding: .4rem .55rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); color: var(--fg); min-width: 9rem; }
 .filters input:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; border-color: var(--accent); }
 .btn { font: inherit; font-weight: 600; padding: .45rem 1rem; border: 1px solid var(--accent); border-radius: var(--radius); background: var(--accent); color: var(--accent-fg); cursor: pointer; }
+/* anchors styled as buttons: the generic a{} / a:visited{} colour rules outrank
+   .btn on <a>, painting the label accent-on-accent (invisible). Restore the
+   button foreground for anchor buttons, visited included. */
+a.btn, a.btn:visited { color: var(--accent-fg); }
 .btn:hover { filter: brightness(1.05); }
 .btn:active { transform: translateY(1px); }