migration: fill in the new box addresses, decide IPv6, add box specs

New box: 179.237.86.116 / 2001:1600:18:206::89, 4CPU/12GB/250GB,
Ubuntu 26.04 LTS, one free snapshot slot, reverse DNS unset on both
addresses. IPv6 exists, so the 18 AAAA records are repointed rather
than deleted.

cloudron-server-migration.md

@@ -53,20 +53,24 @@ needed to restore are inside the thing being restored.
 - [ ] Confirm the backup target's S3 access key is available off-box. The agent host has
       `~/.hermes/security/backup_sites_backup.json` (0600) — check whether it carries the
       key; if not, retrieve it from the Infomaniak console.
-- [ ] New host capacity: `df -h`, `free -m`, `lsb_release -a`, `cloudron --version`.
-      Must hold ~6 GB of app data plus Docker images and growth; check swap exists.
-- [ ] OS: same or newer Ubuntu than the old box. Cloudron install version must be ≥ the
-      old box's (9.0.4).
+- [x] New host capacity: **4 CPU, 12 GB RAM, 250 GB disk** (given 2026-10-30) — ample for
+      ~6 GB of app data plus images. Old box used ~17 GB of 58 GB.
+- [ ] OS: the new box is **Ubuntu 26.04 LTS**. Confirm Cloudron 9.x supports 26.04 *before*
+      installing — an unsupported release can be refused by the installer. Install version
+      must be ≥ the old box's (9.0.4).
 - [ ] Confirm the Cloudron subscription can be moved to a new server.
-- [ ] **Decide the IPv6 question before anything else DNS-related.** The zone carries
+- [ ] **IPv6: DECIDED — repoint.** The new box has `2001:1600:18:206::89`, so all 18
+      AAAA records move with the A records (§3 originally left this open). The zone carries
       **AAAA records on 18 hostnames** — everything that has an A record — all pointing to
       `2a02:4780:6e:83fd::1` (Hostinger's range). Counted 2026-10-30; the full list is in
       `dns-change-sheet.md`. This is 18 deletions or repoints, not a footnote. If the new box has IPv6, repoint them;
       if it does not, **delete the AAAA records** as part of the switch. Changing only
       the A records leaves every IPv6-capable client — including other Matrix
       homeservers and mail senders — still reaching the old box.
-- [ ] Ask Infomaniak to set **rDNS/PTR for the new IP to `my.inference.coop`** — mail
-      deliverability depends on it.
+- [ ] Set **rDNS/PTR → `my.inference.coop` on BOTH `179.237.86.116` and
+      `2001:1600:18:206::89`**. The console lists reverse DNS as unconfigured for both.
+      Not time-sensitive — do it now. If IPv6 sending causes trouble later, disable v6
+      egress for SMTP rather than removing the AAAA.
 - [ ] Open on the new box: **22, 80, 443, 465, 587, 993, and 25 inbound** (mail delivery
       — test from outside, e.g. `telnet my.inference.coop 25` once DNS moves; note that
       many networks block *outbound* 25, so a closed result from inside another server is
@@ -169,7 +173,6 @@ needed to restore are inside the thing being restored.
 - Whether the S3 access key is in the off-box JSON or only inside Cloudron.
 - Whether any provider API key is bound to our current IP.
 - Whether the subscription permits a server move.
-- Whether the new Infomaniak box has IPv6 at all (decides the AAAA action).
 
 ## 8. Pitfalls this server has already produced