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>

README.md

@@ -112,8 +112,8 @@ outbound mail will not reach the real internet without DNS, PTR, and port 25.
 > local image and pulls nothing:
 >
 > ```sh
-> docker build -f build/Dockerfile --build-arg VERSION=2.10.3 \
->   -t ghcr.io/mixeme/selfpost:2.10.3 .
+> docker build -f build/Dockerfile --build-arg VERSION=2.10.4 \
+>   -t ghcr.io/mixeme/selfpost:2.10.4 .
 > ```
 
 ```sh
@@ -122,7 +122,7 @@ docker run --rm -d --name selfpost-try \
   -e SELFPOST_HOSTNAME=mail.local.test \
   -e PANEL_COOKIE_SECURE=false \
   -v selfpost-try-data:/data \
-  ghcr.io/mixeme/selfpost:2.10.3
+  ghcr.io/mixeme/selfpost:2.10.4
 ```
 
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