Rebrand as Playlink with a new sunset theme

- Name: Playlink in the UI, page title, footer, messages and README
  (file names like playlink.db and .playlink-trash are unchanged).
- Theme: plum-black surfaces with a coral-to-pink accent, a soft glow
  behind the page, gradient primary buttons, toggles and progress bars,
  accent focus rings and slim scrollbars.
- New logo (beamed notes on the brand gradient) and a Play/link wordmark.
- Inter variable font, bundled so it works under the strict CSP.

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

web/public/favicon.svg

@@ -1 +1 @@
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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32"><defs><linearGradient id="g" x1="0" y1="0" x2="1" y2="1"><stop offset="0" stop-color="#ff8a5c"/><stop offset="1" stop-color="#ff4f9a"/></linearGradient></defs><rect width="32" height="32" rx="8" fill="url(#g)"/><path d="M12 22V10.5l11-2.5v12" fill="none" stroke="#fff" stroke-width="2.6" stroke-linecap="round" stroke-linejoin="round"/><circle cx="9.4" cy="22" r="3" fill="#fff"/><circle cx="20.4" cy="20" r="3" fill="#fff"/></svg>