Add an nginx version of the /heos proxy

Same contract as the Apache one -- strip the prefix off the request, tell
the app about it with X-Forwarded-Prefix, keep it to the local network --
with the two things nginx needs that Apache did not: a redirect for the
bare /heos, which would otherwise miss the location and fall through to
the filesystem, and the trailing slash on proxy_pass that does the
stripping.

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

README.md

@@ -104,9 +104,9 @@ WantedBy=multi-user.target
 sudo systemctl enable --now heos-panel
 ```
 
-## Behind Apache, at /heos
+## Behind a reverse proxy, at /heos
 
-`deploy/heos.conf` reverse-proxies `/heos` to the panel:
+`deploy/heos.conf` reverse-proxies `/heos` to the panel with Apache:
 
 ```bash
 sudo a2enmod proxy proxy_http headers
@@ -115,11 +115,16 @@ sudo a2enconf heos
 sudo apachectl configtest && sudo systemctl reload apache2
 ```
 
-It ships restricted to the local network — it controls the speakers, and
-it usually hangs off a vhost with a public certificate. Delete the
-`RequireAny` block to open it up.
+`deploy/heos.nginx.conf` is the same thing for nginx: copy it to
+`/etc/nginx/snippets/heos.conf`, `include snippets/heos.conf;` inside the
+`server` block, then `sudo nginx -t && sudo systemctl reload nginx`.
 
-The app works at either address without being told which. Apache sends
+Both ship restricted to the local network — this controls the speakers, and
+it usually hangs off a host with a public certificate. Delete the
+`RequireAny` block (Apache) or the `allow`/`deny` lines (nginx) to open it
+up.
+
+The app works at either address without being told which. The proxy sends
 `X-Forwarded-Prefix: /heos`, and every URL the app generates — stylesheet,
 icons, the manifest's `start_url`, every `fetch` — picks up that prefix.
 Serve it straight from port 5005 and the same URLs come out as `/...`.
@@ -128,8 +133,8 @@ and nothing on it works.
 
 Two things worth knowing:
 
-- The `<Location>` block takes `/heos` away from the filesystem, so the
-  source under `/var/www/html/heos` stops being served as static files.
+- The proxy block takes `/heos` away from the filesystem, so the source
+  under `/var/www/html/heos` stops being served as static files.
 - The panel still answers directly on `<pi-ip>:5005`. Start it with
   `--host 127.0.0.1` if you want Apache to be the only way in.
 

deploy/heos.nginx.conf

@@ -0,0 +1,57 @@
+# HEOS panel behind nginx, at /heos
+#
+#   sudo cp /var/www/html/heos/deploy/heos.nginx.conf /etc/nginx/snippets/heos.conf
+#   then inside the server { } block that serves the site:
+#       include snippets/heos.conf;
+#   sudo nginx -t && sudo systemctl reload nginx
+#
+# nginx reaches the panel on port 5005 (WEB_PORT in config.py). If you want
+# it reachable ONLY through nginx, start it with --host 127.0.0.1; by
+# default it also answers directly on the LAN at <pi-ip>:5005.
+
+# A bare /heos would miss the location below and fall through to the
+# filesystem, so send it to the slashed form first.
+location = /heos {
+    return 301 /heos/;
+}
+
+location /heos/ {
+    # The panel controls the speakers, and it usually hangs off a host
+    # with a public certificate. Keep it to the house unless you mean
+    # otherwise: drop these four lines to let it answer from anywhere.
+    allow 192.168.0.0/24;
+    allow 127.0.0.1;
+    allow ::1;
+    deny all;
+
+    # The trailing slash on proxy_pass is what strips /heos/ back off
+    # before the request reaches the app.
+    proxy_pass http://127.0.0.1:5005/;
+
+    # Tells the app it is mounted on a sub-path, so every link, icon and
+    # fetch it generates is /heos/... rather than /... Without this the
+    # page loads and nothing on it works.
+    proxy_set_header X-Forwarded-Prefix /heos;
+
+    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_http_version 1.1;
+    proxy_set_header Connection "";
+}
+
+# Giving it a host of its own instead? Then it is not on a sub-path, and
+# the X-Forwarded-Prefix line above is the one thing to leave out:
+#
+#   server {
+#       server_name heos.example.com;
+#       location / {
+#           proxy_pass http://127.0.0.1:5005;
+#           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;
+#       }
+#   }