chore: update indiekit-endpoint-activitypub to ba4bb53 (fix oauth token expiry)

Bump AP fork to fix constant re-login on Phanpy. Root cause: the
authorization_code token exchange set accessToken but never $unset expiresAt,
so the 10-min auth-code TTL survived onto the access token, causing all
Mastodon clients to be forced to re-login every 10 minutes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package-lock.json

@@ -2419,7 +2419,7 @@
     },
     "node_modules/@rmdes/indiekit-endpoint-activitypub": {
       "version": "3.13.4",
-      "resolved": "git+https://gitea.giersig.eu/svemagie/indiekit-endpoint-activitypub#2d67c640d7d12c6a6c453b708be295377ba87a91",
+      "resolved": "git+https://gitea.giersig.eu/svemagie/indiekit-endpoint-activitypub#ba4bb53f0d67d0b043d05aa12647672492bb8e7b",
       "license": "MIT",
       "dependencies": {
         "@fedify/debugger": "^2.1.0",