feat: wordmark on every beep + self-hosted Gitea updates (v1.7.0)

- Show the Beep wordmark bottom-right of every beep and reply, beside the
  delete button (delete stays furthest right).
- Add Beep_Updater: WordPress-native plugin updates backed by the Gitea
  releases API, with token auth for the private repo, "View details"
  changelog, archive-folder normalization, and a "Check for updates" link.
- Bump version to 1.7.0; sync readme.txt stable tag + changelog.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/beep.css

@@ -709,6 +709,24 @@
   .beep-embed .beep-feed-header { padding: 12px 16px; }
 }
 
+/* Post footer: wordmark + delete, pinned bottom-right (delete furthest right) */
+.beep-embed .beep-post-footer {
+  display: flex;
+  justify-content: flex-end;
+  align-items: center;
+  gap: 8px;
+  margin-top: 6px;
+}
+.beep-embed .beep-post-wordmark {
+  height: 16px;
+  width: auto;
+  opacity: 0.55;
+  flex: 0 0 auto;
+}
+.beep-embed .beep-reply-footer .beep-post-wordmark {
+  height: 13px;
+}
+
 /* Delete */
 .beep-embed .beep-delete-row { display: flex; justify-content: flex-end; margin-top: 6px; }