feat: deploy en host LXC (nginx + systemd) y ajustes para mismo-origen

- deploy/nginx-host.conf: nginx del host sirve dist/ de las 4 apps y
  proxifica /api/ a 127.0.0.1:3000 (client_max_body_size 10m)
- deploy/frasa-api.service: API Gateway como servicio systemd
- landing: URLs relativas (/quote/, /client/, /pay/)
- Dockerfiles de apps: ARG VITE_API_URL=/api para builds same-origin
- docker-compose: NGINX_CONF parametrizado (nginx.http.conf sin SSL)
- README: instrucciones para host LXC y nota de DDNS pendiente

deploy/nginx-host.conf

@@ -0,0 +1,39 @@
+# FRASA Ecosystem — nginx del host (modo HTTP, LAN)
+# Instalado en /etc/nginx/sites-available/frasa
+server {
+    listen 80 default_server;
+    server_name _;
+
+    client_max_body_size 10m;
+
+    # API Gateway (servicio systemd frasa-api en 127.0.0.1:3000)
+    location /api/ {
+        proxy_pass http://127.0.0.1:3000;
+        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;
+    }
+
+    # Apps estáticas (builds de producción)
+    location /quote/ {
+        alias /root/frasa-ecosystem/apps/cotizador/dist/;
+        try_files $uri $uri/ /quote/index.html;
+    }
+
+    location /client/ {
+        alias /root/frasa-ecosystem/apps/alta-clientes/dist/;
+        try_files $uri $uri/ /client/index.html;
+    }
+
+    location /pay/ {
+        alias /root/frasa-ecosystem/apps/cobranza/dist/;
+        try_files $uri $uri/ /pay/index.html;
+    }
+
+    # Landing (raíz)
+    location / {
+        root /root/frasa-ecosystem/apps/landing/dist;
+        try_files $uri $uri/ /index.html;
+    }
+}