release: 2.10.4: origin-strict - a change with neither header is refused

Cut without asking, as the owner said on 2026-10-15. A POST with neither
Sec-Fetch-Site nor Origin is refused (the commit before this); the e2e
client sends Origin. go vet, go test (26 packages) and make e2e passed on
the test server for that tree. No migration, schema 12.

CHANGELOG [2.10.4]; pins in deploy/docker-compose.yml, README and the guide
(pin, build, the sample restore message); development's "from pin" and
row 36; roadmap row. No tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

deploy/docker-compose.yml

@@ -23,7 +23,7 @@
 
 services:
   selfpost:
-    image: ghcr.io/mixeme/selfpost:2.10.3
+    image: ghcr.io/mixeme/selfpost:2.10.4
     restart: unless-stopped
     environment:
       SELFPOST_HOSTNAME: "${SELFPOST_HOSTNAME:?set the mail/panel hostname, e.g. mail.example.com}"