FASE 7: Quick Wins de Performance — Optimización Fase 1

Cambios implementados:

1. Nginx:
   - gzip on (compresión JS/CSS/JSON)
   - Cache headers para assets estáticos (6M)
   - Proxy buffer tuning (10s connect, 30s read)

2. Frontend catalog.js:
   - Reemplazados 8x innerHTML += en loops por map+join
   - Event delegation en breadcrumb y cart (elimina memory leak)
   - AbortController en apiFetch (evita race conditions)
   - sessionStorage cache para years-all y brands por modo

3. Frontend templates HTML:
   - defer en todos los scripts POS (mejora First Paint)

4. Dashboard JS:
   - innerHTML += fix en dashboard.js y cuentas.js

5. Base de datos:
   - Índice parcial idx_wi_part_stock_positive en warehouse_inventory

6. Documentación:
   - docs/performance_audit_2026.md con análisis completo y roadmap

Tests: 73/73 pasando (compat + fase3 + fase5 + fase6)

nginx/nexus-pos.conf

@@ -13,17 +13,37 @@ upstream nexus_pos {
     server 127.0.0.1:5001;
 }
 
+# Gzip compression
+gzip on;
+gzip_vary on;
+gzip_proxied any;
+gzip_comp_level 6;
+gzip_types text/plain text/css text/xml application/json application/javascript application/rss+xml application/atom+xml image/svg+xml;
+
 # Main site (no subdomain)
 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;
+    }
+
     location / {
         proxy_pass http://nexus_main;
         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;
+        proxy_connect_timeout 10s;
+        proxy_send_timeout 30s;
+        proxy_read_timeout 30s;
+        proxy_buffering on;
+        proxy_buffer_size 4k;
+        proxy_buffers 8 4k;
     }
 }
 
@@ -36,6 +56,13 @@ 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)$ {
+        expires 6M;
+        add_header Cache-Control "public, immutable";
+        add_header X-Content-Type-Options nosniff always;
+    }
+
     location / {
         proxy_pass http://nexus_pos;
         proxy_set_header Host $host;
@@ -43,6 +70,12 @@ server {
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
         proxy_set_header X-Tenant-Subdomain $tenant;
+        proxy_connect_timeout 10s;
+        proxy_send_timeout 30s;
+        proxy_read_timeout 30s;
+        proxy_buffering on;
+        proxy_buffer_size 4k;
+        proxy_buffers 8 4k;
     }
 
     # Rate limit login endpoint