Compress the bundle in the nginx example

The Caddy example has `encode zstd gzip`; the nginx one had nothing, so a
deployment following it shipped every asset uncompressed. Measured against the
built app that is 915 KB on the wire where 307 KB would do -- the difference
falls entirely on first load, and silently, since nothing about it is visible
without inspecting response headers.

`text/javascript` is listed explicitly. The server sends scripts with that
type rather than `application/javascript`, so a conventional gzip_types list
compresses the stylesheet and leaves the 647 KB script alone -- which is what
happened on the first attempt at this change.

text/event-stream is deliberately not listed. Compressing or buffering the
push stream would break it; proxy_buffering is already off below for the same
reason. Verified that /api/events still delivers a StateChange event through
the proxy, as plain text, while assets come back gzipped with Vary set.

nginx.example.conf

@@ -6,6 +6,26 @@ server {
 
     client_max_body_size 60m;
 
+    # ihasmail serves its bundle uncompressed and leaves this to the proxy, so
+    # without these directives the browser downloads about 915 KB where 307 KB
+    # would do. text/event-stream is deliberately absent from gzip_types: the
+    # push stream must not be compressed or buffered.
+    gzip on;
+    gzip_vary on;
+    gzip_proxied any;
+    gzip_comp_level 5;
+    gzip_min_length 1024;
+    # ihasmail serves scripts as text/javascript, so listing only
+    # application/javascript silently leaves the largest asset uncompressed.
+    gzip_types
+        application/javascript
+        application/json
+        application/manifest+json
+        image/svg+xml
+        text/css
+        text/javascript
+        text/plain;
+
     location / {
         proxy_pass http://127.0.0.1:8080;
         proxy_http_version 1.1;