release: 2.10.0: inbound-upstream-result - the upstream's answer in the Inbound log

Cut at the owner's word (2026-10-16): "потом режь" after the check, which
he allowed ("Отправляй").

Inbound › Log says what became of accepted mail - queued, held, sent,
deferred, bounced - with the upstream's last reply, the host and when
(5348330, 295d72e, 46b90d2 design and plan; d515493 code, the reviews'
findings fixed in it). Migration 0012, schema 12.

On the test server as 2.9.1-post.d515493 (the same code), 2026-10-16:
healthy, every program RUNNING, keys unchanged, schema 12. One message
sent from the server to its own port 25 for selfpost@dev.mixdep.ru: its
row sent, "250 2.0.0 Ok: queued as 04F0D1023EF" from mc-ent.mixfed.ru. (The
owner's own message had gone to mc-ent directly: SelfPost is
dev.mixdep.ru's second MX.)

CHANGELOG [2.10.0]; pins in deploy/docker-compose.yml, README and the guide
(pin, build, the sample restore message); development's "from pin" and row
32; roadmap row and recommended order; plan closed. No tag.

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

docs/guide.md

@@ -204,14 +204,14 @@ cat ./data/setup-token
 #### Fixed image tag
 
 `deploy/docker-compose.yml` pins an explicit version (`ghcr.io/mixeme/selfpost:X.Y.Z`),
-deliberately never `:latest`. The current pin is `2.9.1`. **No 2.x image is
+deliberately never `:latest`. The current pin is `2.10.0`. **No 2.x image is
 published on ghcr.io yet** (the newest there is `1.3.0`); until one is, build
 it from the checkout under the pinned name, and Compose uses the local image
 instead of pulling:
 
 ```sh
-docker build -f build/Dockerfile --build-arg VERSION=2.9.1 \
-  -t ghcr.io/mixeme/selfpost:2.9.1 .
+docker build -f build/Dockerfile --build-arg VERSION=2.10.0 \
+  -t ghcr.io/mixeme/selfpost:2.10.0 .
 ```
 
 `VERSION` must equal the tag: it is the version the backup check compares
@@ -944,7 +944,7 @@ A version mismatch at step 5 refuses to start and leaves `/data` untouched —
 the panel exits with a message naming the tag to use, e.g.:
 
 ```
-backup: this backup was created by SelfPost 2.9.0 but this image is 2.9.1 — restore into the matching image (selfpost:2.9.0)
+backup: this backup was created by SelfPost 2.9.1 but this image is 2.10.0 — restore into the matching image (selfpost:2.9.1)
 ```
 
 Fix the tag in `docker-compose.yml` (build that tag as under [Fixed image