Serve the same court twice, so staging can be tried before the crowd arrives

The image now answers at /staging/ as well as /, via an alias to the same
root — that way the staging deploy works whether or not Coolify strips the
path prefix, and the staging branch needs no diff of its own to merge.

The manifest MIME moved from an exact-match location into the stock types
map: an exact match would have missed the /staging/ copy, and a regex
location would have out-ranked the prefix and resolved against root.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Dockerfile

@@ -1,9 +1,14 @@
 FROM nginx:alpine
 # no-cache => browsers revalidate every request (ETag 304s are cheap), so a new
 # deploy is picked up on plain reload. ponytail: switch to hashed filenames if traffic ever matters.
-# The exact-match location gives the manifest its own MIME type — nginx's default map has no
-# .webmanifest entry and Chrome refuses to install a homescreen app served as octet-stream.
-# (a bare `types {}` block would have REPLACED the whole map and broken .js/.png too.)
-RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  etag on;\n  location = /manifest.webmanifest { default_type application/manifest+json; add_header Cache-Control "no-cache, must-revalidate"; }\n  location / { add_header Cache-Control "no-cache, must-revalidate"; }\n}\n' > /etc/nginx/conf.d/default.conf
+# nginx's default map has no .webmanifest entry and Chrome refuses to install a homescreen app
+# served as octet-stream, so we append the type to the stock map. It has to be the map and not a
+# `location`: an exact match misses the /staging/ copy below, and a regex match would out-rank the
+# /staging/ prefix and resolve against root instead of the alias. A local `types {}` block is out
+# too — it REPLACES the whole map (breaking .js/.png), and mime.types can't be re-included inside one.
+RUN sed -i 's#^}#    application/manifest+json  webmanifest;\n}#' /etc/nginx/mime.types
+# The /staging/ alias serves the SAME files one level down, so the staging deploy works whether or
+# not Coolify/Traefik strips the path prefix. Identical on every branch => never a merge conflict.
+RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  etag on;\n  index index.html;\n  absolute_redirect off;\n  location = /staging { return 301 /staging/; }\n  location /staging/ { alias /usr/share/nginx/html/; add_header Cache-Control "no-cache, must-revalidate"; }\n  location / { add_header Cache-Control "no-cache, must-revalidate"; }\n}\n' > /etc/nginx/conf.d/default.conf
 COPY index.html manifest.webmanifest *.js /usr/share/nginx/html/
 COPY assets /usr/share/nginx/html/assets