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/gpu/start_gpu_miner.sh

@@ -1,32 +0,0 @@
-#!/bin/bash
-# Start GPU Miner Client
-
-echo "=== AITBC GPU Miner Client Startup ==="
-echo "Starting GPU miner client..."
-echo ""
-
-# Check if GPU is available
-if ! command -v nvidia-smi &> /dev/null; then
-    echo "WARNING: nvidia-smi not found, GPU may not be available"
-fi
-
-# Show GPU info
-if command -v nvidia-smi &> /dev/null; then
-    echo "=== GPU Status ==="
-    nvidia-smi --query-gpu=name,memory.used,memory.total,utilization.gpu,temperature.gpu --format=csv,noheader,nounits
-    echo ""
-fi
-
-# Check if coordinator is running
-echo "=== Checking Coordinator API ==="
-if curl -s http://localhost:8000/health > /dev/null 2>&1; then
-    echo "✓ Coordinator API is running on port 8000"
-else
-    echo "✗ Coordinator API is not accessible on port 8000"
-    echo "  The miner will wait for the coordinator to start..."
-fi
-
-echo ""
-echo "=== Starting GPU Miner ==="
-cd /home/oib/windsurf/aitbc
-python3 gpu_miner_with_wait.py