Generate IndexNow keys + wire into each docs site (preset 3.8.0+ ready)

[rubenvdlinde]

Part of #75 (SEO epic).

What

Generate one IndexNow key per Conduction property (18 total) and paste it into each site's docusaurus.config.js so the preset's IndexNow plugin pings api.indexnow.org on every successful build. Bing recrawls within minutes; the AI surfaces it feeds (Copilot, ChatGPT Search, DuckDuckGo) follow.

Why

Without IndexNow, Bing's recrawl latency is 1–4 weeks. That's the dominant non-Google index for AI assistants in 2026. With it, content changes hit AI surfaces same-day.

How

Per property:

1. Generate a 64-char key at https://www.bing.com/indexnow/getstarted. Save the key (one per host is fine).
2. Add to the site's docusaurus.config.js:

   indexnow: {
     key: 'abc123...',
   }

3. Commit + push. The preset's postBuild plugin writes <key>.txt to the build output (verification handshake) and POSTs the sitemap URL list to api.indexnow.org on the next deploy.

Properties

Same list as #74 (18 sites: www.conduction.nl + 17 *.conduction.nl).

Verification per site

• After deploy, https://<site>/<key>.txt returns 200 with the key as plaintext.
• Build logs show [indexnow] submitted N URLs to api.indexnow.org (200).
• Bing Webmaster Tools "Submit URLs" section shows IndexNow activity (after ~24h).