fix: use existing default-avatar.svg instead of missing placeholder-avatar.png

The fallback avatar URL pointed to /placeholder-avatar.png which doesn't
exist (404). Changed to /images/default-avatar.svg which exists in the
Eleventy theme and is served by the nginx image caching location with
CORS headers — fixing cross-origin errors in Phanpy/Elk.

lib/mastodon/entities/account.js

@@ -95,8 +95,8 @@ export function serializeAccount(actor, { baseUrl, isLocal = false, handle = ""
     url,
     display_name: displayName,
     note: sanitizeHtml(note),
-    avatar: avatarUrl || `${baseUrl}/placeholder-avatar.png`,
-    avatar_static: avatarUrl || `${baseUrl}/placeholder-avatar.png`,
+    avatar: avatarUrl || `${baseUrl}/images/default-avatar.svg`,
+    avatar_static: avatarUrl || `${baseUrl}/images/default-avatar.svg`,
     header: headerUrl || "",
     header_static: headerUrl || "",
     locked: actor.manuallyApprovesFollowers || false,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-activitypub",
-  "version": "3.5.7",
+  "version": "3.5.8",
   "description": "ActivityPub federation endpoint for Indiekit via Fedify. Adds full fediverse support: actor, inbox, outbox, followers, following, syndication, and Mastodon migration.",
   "keywords": [
     "indiekit",