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

website/aitbc-proxy.conf

@@ -1,57 +0,0 @@
-server {
-    listen 80;
-    listen [::]:80;
-    server_name aitbc.bubuit.net localhost;
-    
-    # Forward all requests to the AITBC container
-    location / {
-        proxy_pass http://10.1.223.93;
-        proxy_set_header Host $host;
-        proxy_set_header X-Real-IP $remote_addr;
-        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-        proxy_set_header X-Forwarded-Proto $scheme;
-        
-        # WebSocket support
-        proxy_http_version 1.1;
-        proxy_set_header Upgrade $http_upgrade;
-        proxy_set_header Connection "upgrade";
-        
-        # Timeouts
-        proxy_connect_timeout 60s;
-        proxy_send_timeout 60s;
-        proxy_read_timeout 60s;
-        
-        # Buffer settings
-        proxy_buffering on;
-        proxy_buffer_size 4k;
-        proxy_buffers 8 4k;
-    }
-    
-    # Health check endpoint
-    location /health {
-        proxy_pass http://10.1.223.93/health;
-        access_log off;
-    }
-    
-    # Logging
-    access_log /var/log/nginx/aitbc-proxy.access.log;
-    error_log /var/log/nginx/aitbc-proxy.error.log;
-}
-
-# HTTPS configuration (for future SSL setup)
-# server {
-#     listen 443 ssl http2;
-#     listen [::]:443 ssl http2;
-#     server_name aitbc.bubuit.net;
-#     
-#     ssl_certificate /etc/ssl/certs/aitbc.bubuit.net.crt;
-#     ssl_certificate_key /etc/ssl/private/aitbc.bubuit.net.key;
-#     
-#     location / {
-#         proxy_pass http://10.1.223.93;
-#         proxy_set_header Host $host;
-#         proxy_set_header X-Real-IP $remote_addr;
-#         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
-#         proxy_set_header X-Forwarded-Proto $scheme;
-#     }
-# }