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/deploy/test-deployment.sh

@@ -1,40 +0,0 @@
-#!/bin/bash
-
-# Test if blockchain node and explorer are running
-
-echo "🔍 Testing Blockchain Deployment"
-echo "==============================="
-
-# Test blockchain RPC
-echo "Testing blockchain RPC..."
-if curl -s http://aitbc.keisanki.net:8082/rpc/head > /dev/null; then
-    echo "✅ Blockchain RPC is accessible"
-    curl -s http://aitbc.keisanki.net:8082/rpc/head | jq '.height'
-else
-    echo "❌ Blockchain RPC is not accessible"
-fi
-
-# Test explorer
-echo ""
-echo "Testing blockchain explorer..."
-if curl -s http://aitbc.keisanki.net:3000 > /dev/null; then
-    echo "✅ Explorer is accessible"
-else
-    echo "❌ Explorer is not accessible"
-fi
-
-# Check services on server
-echo ""
-echo "Checking service status on ns3..."
-ssh ns3-root "systemctl is-active blockchain-node blockchain-rpc nginx" | while read service status; do
-    if [ "$status" = "active" ]; then
-        echo "✅ $service is running"
-    else
-        echo "❌ $service is not running"
-    fi
-done
-
-# Check logs if needed
-echo ""
-echo "Recent blockchain logs:"
-ssh ns3-root "journalctl -u blockchain-node -n 5 --no-pager"