Mastodon nginx: use `@soapbox` named location for consistency

installation/mastodon.conf

@@ -14,7 +14,7 @@ map $http_upgrade $connection_upgrade {
 
 # ActivityPub routing.
 map $http_accept $activitypub_location {
-  default /index.html;
+  default @soapbox;
   "application/activity+json" @proxy;
   'application/ld+json; profile="https://www.w3.org/ns/activitystreams"' @proxy;
 }
@@ -71,7 +71,7 @@ server {
   add_header Strict-Transport-Security "max-age=31536000" always;
 
   # Fallback route.
-  # Everything not routed should fall back to the SPA.
+  # Try static files, then fall back to the SPA.
   location / {
     try_files /dev/null @static-files;
   }
@@ -85,7 +85,7 @@ server {
   # Mastodon ActivityPub routes.
   # Conditionally send to Mastodon by Accept header.
   location ~ ^/(inbox|users|@(.+)) {
-    try_files $activitypub_location $activitypub_location;
+    try_files /dev/null $activitypub_location;
   }
 
   # Soapbox & Mastodon (frontend) build files.
@@ -108,11 +108,16 @@ server {
     add_header Strict-Transport-Security "max-age=31536000" always;
   }
 
-  # Mastodon public files.
+  # Soapbox SPA (Single Page App).
+  location @soapbox {
+    try_files /index.html /dev/null;
+  }
+
+  # Mastodon public files (fallback to Soapbox SPA).
   # https://github.com/mastodon/mastodon/tree/main/public
   location @mastodon-public {
     root /home/mastodon/live/public;
-    try_files $uri /index.html;
+    try_files $uri @soapbox;
   }
 
   # Soapbox & Mastodon static files.