feat(whatsapp): QWEN primary AI backend, Hermes fallback, conversation history, vehicle persistence, demo prompts

- Add QWEN (qwen3.6) as primary AI backend with short system prompt
- Hermes remains as fallback with 45s timeout
- Increase QWEN timeout to 35s, max_tokens to 4000
- Add conversation history loading from whatsapp_messages (last 4 msgs)
- Persist detected vehicle in whatsapp_sessions table
- Add 'limpiar chat' / 'nuevo chat' / 'reset' commands to clear history
- Fix CSS conflict: rename whatsapp chat-panel classes to wa-chat-panel
- Fix JS ID conflicts with chat.js widget (waChatPanel, waChatMessages, etc.)
- Improve no-stock response: conversational with alternatives
- Split search_query by | for multi-part lookups
- Add DEMO_PROMPTS.md and DEMO_PROMPTS_V2.md

nginx/nexus-pos.conf

@@ -29,26 +29,14 @@ server {
     listen 80;
     server_name nexusautoparts.com www.nexusautoparts.com;
 
-    # Static asset caching
-    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
-        expires 6M;
-        add_header Cache-Control "public, immutable";
-        add_header X-Content-Type-Options nosniff always;
-    }
-
-    # Auto-serve minified JS/CSS when available (transparent to templates)
-    location ~* ^(.+)\.js$ {
-        try_files $1.min.js $uri =404;
-        expires 6M;
-        add_header Cache-Control "public, immutable";
-        add_header X-Content-Type-Options nosniff always;
-    }
-
-    location ~* ^(.+)\.css$ {
-        try_files $1.min.css $uri =404;
+    # POS static assets — served directly by nginx (not proxied)
+    # ^~ prevents regex locations from intercepting these requests
+    location ^~ /pos/static/ {
+        alias /home/Autopartes/pos/static/;
         expires 6M;
         add_header Cache-Control "public, immutable";
         add_header X-Content-Type-Options nosniff always;
+        access_log off;
     }
 
     location / {
@@ -75,11 +63,14 @@ server {
     add_header X-Content-Type-Options nosniff always;
     add_header X-Frame-Options SAMEORIGIN always;
 
-    # Static asset caching
-    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+    # POS static assets — served directly by nginx (not proxied)
+    # ^~ prevents regex locations from intercepting these requests
+    location ^~ /pos/static/ {
+        alias /home/Autopartes/pos/static/;
         expires 6M;
         add_header Cache-Control "public, immutable";
         add_header X-Content-Type-Options nosniff always;
+        access_log off;
     }
 
     location / {