feat(deploy): build + serve worker and admin as static nginx images

- per-app Dockerfiles (vite build → nginx) + SPA nginx.conf
- Gitea workflow pushes 3 images; frontends bake VITE_API_URL
- docker-compose.prod.yml (registry images, solelog_network) + .env.prod.example
- docker-compose.yml runs the full stack locally; add .dockerignore

apps/worker/nginx.conf

@@ -0,0 +1,23 @@
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    gzip on;
+    gzip_types text/css application/javascript application/json image/svg+xml;
+
+    # Hashed build assets are immutable — cache them hard.
+    location /assets/ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+        try_files $uri =404;
+    }
+
+    # SPA fallback: any unknown path serves index.html so React Router can
+    # handle it client-side (deep links and refreshes work). Never cache the shell.
+    location / {
+        try_files $uri $uri/ /index.html;
+        add_header Cache-Control "no-cache";
+    }
+}