feat: auto-inject chat widget on all storefronts via Shopify ScriptTag API

- auth.js: register chat widget ScriptTag during OAuth callback so every
  new install automatically gets the floating chat button — no manual
  theme editing required
- server.js: GET /chat/backfill-scripttags endpoint to register the widget
  on all already-installed shops in one hit

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

auth.js

@@ -38,7 +38,30 @@ router.get('/auth/callback', async (req, res) => {
     saveToken(shop, access_token, scope);
     log(shop, '💾 Token saved to data/tokens.json');
 
-    // 2) Create fulfillment service (existing step)
+    // 2) Register chat widget ScriptTag so it auto-injects on every storefront page
+    try {
+      const WIDGET_SRC = `https://backend.data4autos.com/chat/widget.js?shop=${encodeURIComponent(shop)}`;
+      // Check if already registered to avoid duplicates
+      const existingResp = await axios.get(
+        `https://${shop}/admin/api/2025-10/script_tags.json?src=${encodeURIComponent(WIDGET_SRC)}`,
+        { headers: { 'X-Shopify-Access-Token': access_token, 'Content-Type': 'application/json' } }
+      );
+      const already = existingResp.data?.script_tags?.length > 0;
+      if (!already) {
+        await axios.post(
+          `https://${shop}/admin/api/2025-10/script_tags.json`,
+          { script_tag: { event: 'onload', src: WIDGET_SRC } },
+          { headers: { 'X-Shopify-Access-Token': access_token, 'Content-Type': 'application/json' } }
+        );
+        log(shop, '💬 Chat widget ScriptTag registered on storefront');
+      } else {
+        log(shop, '💬 Chat widget ScriptTag already registered, skipping');
+      }
+    } catch (stErr) {
+      log(shop, `⚠️ ScriptTag registration failed (non-fatal): ${stErr.message}`);
+    }
+
+    // 3) Create fulfillment service (existing step)
     const { fulfillmentService, locationId } = await createFulfillmentService(shop, access_token);
     console.log(`Custom Location created: ${locationId}`);
     saveToken(shop, access_token, scope, fulfillmentService, locationId);

server.js

@@ -108,6 +108,29 @@ app.get('/chat/widget.js', (req, res) => {
 })();`);
 });
 
+// One-time backfill: register chat widget ScriptTag on all already-installed shops
+// Hit: GET /chat/backfill-scripttags  (admin use only — no sensitive data exposed)
+app.get('/chat/backfill-scripttags', async (req, res) => {
+  const { getToken, listTokens } = require('./tokenStore');
+  const axios = require('axios');
+  const stores = listTokens();
+  const results = [];
+  for (const [shop, record] of Object.entries(stores)) {
+    if (!record.accessToken) { results.push({ shop, status: 'no-token' }); continue; }
+    const WIDGET_SRC = `https://backend.data4autos.com/chat/widget.js?shop=${encodeURIComponent(shop)}`;
+    const headers = { 'X-Shopify-Access-Token': record.accessToken, 'Content-Type': 'application/json' };
+    try {
+      const ex = await axios.get(`https://${shop}/admin/api/2025-10/script_tags.json?src=${encodeURIComponent(WIDGET_SRC)}`, { headers });
+      if (ex.data?.script_tags?.length > 0) { results.push({ shop, status: 'already-exists' }); continue; }
+      await axios.post(`https://${shop}/admin/api/2025-10/script_tags.json`, { script_tag: { event: 'onload', src: WIDGET_SRC } }, { headers });
+      results.push({ shop, status: 'registered' });
+    } catch (e) {
+      results.push({ shop, status: 'error', error: e.response?.data || e.message });
+    }
+  }
+  res.json({ results });
+});
+
 // Health check
 app.get('/health', (req, res) => {
   res.json({ ok: true, uptime: process.uptime(), timestamp: new Date().toISOString() });