docs: website widget operations guide + archive widget source

- Comprehensive docs: embed snippet, key management, API endpoints,
  chat/booking/contact flows, lead dedup, reCAPTCHA, branding, deploy
  checklist, troubleshooting
- Widget Preact source archived in packages/widget-src/ (was only on
  local machine, not tracked in any repo)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/widget-src/vite.config.ts

@@ -0,0 +1,22 @@
+import { defineConfig } from 'vite';
+import preact from '@preact/preset-vite';
+
+export default defineConfig({
+    plugins: [preact()],
+    build: {
+        lib: {
+            entry: 'src/main.tsx',
+            name: 'HelixWidget',
+            fileName: () => 'widget.js',
+            formats: ['iife'],
+        },
+        outDir: '../../helix-engage-server/public',
+        emptyOutDir: false,
+        minify: 'esbuild',
+        rollupOptions: {
+            output: {
+                inlineDynamicImports: true,
+            },
+        },
+    },
+});