docs: restructure website, optimize HTML, gitignore private files

Website docs (website/docs/):
- Delete 6 stale -md.html duplicates
- Rename docs-clients/miners/developers → clients/miners/developers.html
- Unify header/nav across all 15 pages (new .site-header pattern)
- Fix 34 dead href=# links with real targets
- Upgrade Font Awesome v4→v6 in index.html
- Replace search stub with live client-side search (15-page index)
- Extract all inline CSS into shared docs.css (+630 lines)
- Extract inline theme JS into shared theme.js
- Strip inline style= attributes from 10+ pages
- Add .announce-banner, .source-links, .search-results CSS classes
- Add Markdown Source links to clients/miners/developers pages
- Update components.html title to Architecture & Components
- Move browser-wallet.html to website/wallet/, leave redirect
- Update all dates to February 2026

Website root:
- Delete 6 root-level duplicate HTML files (160KB saved)
- Rewire index.html and 404.html links

Root README.md:
- Fix 8 broken doc links to new numbered folder structure
- Update copyright to 2026

.gitignore + .example files:
- Gitignore private files: .aitbc.yaml, .env, deploy scripts,
  GPU scripts, service scripts, infra configs, .windsurf/, website README
- Create 7 .example files for GitHub users with sanitized templates
- Untrack 47 previously committed private files

Live server:
- Push all website files to aitbc-cascade:/var/www/html/
- Clean stale admin.html and index.nginx-debian.html

scripts/service/setup-production-assets.sh

@@ -1,40 +0,0 @@
-#!/bin/bash
-
-# Download production assets locally
-echo "Setting up production assets..."
-
-# Create assets directory
-mkdir -p /home/oib/windsurf/aitbc/assets/{css,js,icons}
-
-# Download Tailwind CSS (production build)
-echo "Downloading Tailwind CSS..."
-curl -L https://unpkg.com/tailwindcss@3.4.0/lib/tailwind.js -o /home/oib/windsurf/aitbc/assets/js/tailwind.js
-
-# Download Axios
-echo "Downloading Axios..."
-curl -L https://unpkg.com/axios@1.6.2/dist/axios.min.js -o /home/oib/windsurf/aitbc/assets/js/axios.min.js
-
-# Download Lucide icons
-echo "Downloading Lucide..."
-curl -L https://unpkg.com/lucide@latest/dist/umd/lucide.js -o /home/oib/windsurf/aitbc/assets/js/lucide.js
-
-# Create a custom Tailwind build with only used classes
-cat > /home/oib/windsurf/aitbc/assets/tailwind.config.js << 'EOF'
-module.exports = {
-  content: [
-    "./apps/trade-exchange/index.html",
-    "./apps/marketplace-ui/index.html"
-  ],
-  darkMode: 'class',
-  theme: {
-    extend: {},
-  },
-  plugins: [],
-}
-EOF
-
-echo "Assets downloaded to /home/oib/windsurf/aitbc/assets/"
-echo "Update your HTML files to use local paths:"
-echo "  - /assets/js/tailwind.js"
-echo "  - /assets/js/axios.min.js"
-echo "  - /assets/js/lucide.js"