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/start_dashboard.sh

@@ -1,39 +0,0 @@
-#!/bin/bash
-
-echo "=== Starting AITBC Miner Dashboard ==="
-echo ""
-
-# Find available port
-PORT=8080
-while [ $PORT -le 8090 ]; do
-    if ! netstat -tuln 2>/dev/null | grep -q ":$PORT "; then
-        echo "✓ Found available port: $PORT"
-        break
-    fi
-    echo "Port $port is in use, trying next..."
-    PORT=$((PORT + 1))
-done
-
-if [ $PORT -gt 8090 ]; then
-    echo "❌ No available ports found between 8080-8090"
-    exit 1
-fi
-
-# Start the dashboard
-echo "Starting dashboard on port $PORT..."
-nohup python3 -m http.server $PORT --bind 0.0.0.0 > dashboard.log 2>&1 &
-PID=$!
-
-echo ""
-echo "✅ Dashboard is running!"
-echo ""
-echo "Access URLs:"
-echo "  Local:    http://localhost:$PORT"
-echo "  Network:  http://$(hostname -I | awk '{print $1}'):$PORT"
-echo ""
-echo "Dashboard file: miner-dashboard.html"
-echo "Process ID: $PID"
-echo "Log file: dashboard.log"
-echo ""
-echo "To stop: kill $PID"
-echo "To view logs: tail -f dashboard.log"