release: 2.16.0: the queues as tables

Outbound › Queue is the table the 2.0 mockup drew, and Inbound › Queue is
built (6db3704, design 629de5e, guards 8525e8e, e2e 853e0ca); the Overview
card names both queues; TestUnbuiltScreensAreOnTheRoadmap keeps a deferred
screen from being forgotten again. With it, two gaps the comparison of every
mockup found (6edf831). No migration, schema 14.

CHANGELOG section; pins in deploy/docker-compose.yml, README (build note)
and the guide (pin, build, the backup example). 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=2.15.0 \
->   -t ghcr.io/mixeme/selfpost:2.15.0 .
+> docker build -f build/Dockerfile --build-arg VERSION=2.16.0 \
+>   -t ghcr.io/mixeme/selfpost:2.16.0 .
 > ```
 
 ```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:2.15.0
+  ghcr.io/mixeme/selfpost:2.16.0
 ```
 
 This trial runs with Docker's default capabilities and no