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

.gitignore

@@ -193,3 +193,36 @@ docs/infrastructure.md
 # Workflow files (personal, change frequently)
 docs/1_project/3_currenttask.md
 docs/1_project/4_currentissue.md
+
+# ===================
+# Website (local deployment details)
+# ===================
+website/README.md
+website/aitbc-proxy.conf
+
+# ===================
+# Local Config & Secrets
+# ===================
+.aitbc.yaml
+apps/coordinator-api/.env
+
+# ===================
+# Windsurf IDE (personal dev tooling)
+# ===================
+.windsurf/
+
+# ===================
+# Deploy Scripts (hardcoded local paths & IPs)
+# ===================
+scripts/deploy/*
+!scripts/deploy/*.example
+scripts/gpu/*
+!scripts/gpu/*.example
+scripts/service/*
+
+# ===================
+# Infra Configs (production IPs & secrets)
+# ===================
+infra/nginx/nginx-aitbc*.conf
+infra/helm/values/prod/
+infra/helm/values/prod.yaml