MariaDB finishes its own conversion: MARIADB_AUTO_UPGRADE=1 on the four db services (R-459)

bookstack-db, kimai-db, nextcloud-db, romm-db each gain `MARIADB_AUTO_UPGRADE=1` in the db
service's environment list. Operator ruling 2026-09-13 on the measurement in
felhom.eu/documentation/audits/SPIKE-r459-mariadb-upgrade-2026-09-06.md: an unconverted datadir
is stable but never heals; the conversion costs ~7 s and the engine backs its system tables up
first. MARIADB_DISABLE_UPGRADE_BACKUP is deliberately left UNSET — that backup is the precaution.

NO `image:` line changed, so `catalog_since` does NOT move — the CLAUDE.md rule ties it to an
image change and this is not one. Do not "fix" that.

The setting is inert until an engine major actually moves, and none may until Slice 4 (R-448)
ships — see the engine-major rule in CLAUDE.md and scripts/check-engine-major.py (next commit).
The eleven PostgreSQL templates are untouched: R-463 is a different engine and a different
measurement.

REUSE.md: one convention row for the MariaDB sidecar env, same commit.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

templates/romm/docker-compose.yml

@@ -97,6 +97,11 @@ services:
       - MYSQL_USER=romm
       - MYSQL_PASSWORD=${DB_PASSWORD}
       - TZ=Europe/Budapest
+      # MARIADB_AUTO_UPGRADE: on a MAJOR engine move the engine converts its own datadir (~7 s on a
+      # small DB, backs its system tables up first). Operator ruling 2026-09-13 on
+      # felhom.eu/documentation/audits/SPIKE-r459-mariadb-upgrade-2026-09-06.md. Inert until a
+      # major moves — and none may, until Slice 4 (R-448) ships: see CLAUDE.md, engine-major rule.
+      - MARIADB_AUTO_UPGRADE=1
     volumes:
       - romm_db_data:/var/lib/mysql
     networks: