feat(backup): prod shares dev's MinIO — plus the path tenancy that makes it survivable

Operator ruling: "the S3 backup location is the same as Dev." Prod's
S3_BACKUP_ENDPOINT is now http://192.168.1.9:9000 and the TBD-PROD-* placeholder
is retired. Set EXPLICITLY rather than by omitting the op — an omitted op would
inherit the same value silently, and a shared backup target must be visible in
the overlay that owns it.

SHARING THE ENDPOINT WAS NOT SAFE AS AUTHORED. Nothing about the backup PATHS
was per-environment, and enabling prod against dev's MinIO would have been the
2026-09-04 external-dns incident again, in a worse place:

  VELERO — bucket `velero`, NO prefix, and both clusters run schedules named
    `daily` / `daily-resources-only`. Velero SYNCS backups it finds in its BSL
    into itself as Backup CRs and GARBAGE-COLLECTS them at TTL, so prod would
    have adopted dev's backups and then deleted them on schedule.
  CNPG — the worse one. destinationPath `s3://cnpg` with CNPG appending
    serverName, which defaults to the CLUSTER NAME. Both environments have
    keycloak-db, nextcloud-db and semaphore-db, so prod's Postgres would archive
    WAL into the EXACT prefix dev's does. Two servers interleaving WAL into one
    Barman stream CORRUPTS THE CHAIN and destroys PITR — and dev's restore is
    PROVEN (R-STATE-03). Sharing an endpoint is fine; sharing a path is not.

Two knobs, authored once, environments differing only by scoped overrides
(R-ENV-02):
  VELERO_BACKUP_PREFIX  dev ""          | prod "prod"
  CNPG_BACKUP_PATH      dev "s3://cnpg" | prod "s3://cnpg/prod"

THE BASE VALUES ARE DEV'S CURRENT LAYOUT ON PURPOSE. Dev's existing backups live
at the bucket root and at s3://cnpg; giving dev a prefix would ORPHAN the very
backups its proven restore depends on — the same reasoning that keeps dev's
EXTERNALDNS_TXT_OWNER_ID at `default`. Prod has no history to preserve.

*** PROD STILL HAS NO BACKUP COVERAGE — the endpoint is not reachable. ***
Measured from a throwaway pod INSIDE the prod cluster (the workstation proves
nothing about pod egress, and a workstation-side reading has already misled this
project once): curl http://192.168.1.9:9000/minio/health/live → connection timed
out after 15s. pfSense does not route prod's pod network to the dev LAN's MinIO.
OPERATOR ACTION REQUIRED. velero stays suspended; note apps-wave-0 applies GREEN
regardless — the token IS defined so strict substitution succeeds — while every
write fails at RUNTIME. A green apps-wave-0 does not mean backups work.

New `standup.sh s3check` step probes the endpoint from a throwaway in-cluster
pod and fails closed, with `--s3-endpoint <url>` to test a CANDIDATE before
authoring it into cluster-vars. That is how the unreachability above was
established rather than assumed.

VERIFIED: full CI gate PASS. flux-postbuild-substitution 254 -> 260 assertions,
and neither new knob appears in the dead-knob advisory list, so both are really
consumed. Rendered both overlays: all three CNPG destinationPaths and Velero's
prefix carry the tokens; dev resolves to its existing layout, prod to the nested
paths.

DELIVERY: prod reconciles the bootstrap Gitea's main at c8c1d29. This branch also
carries the DNS inversion, which must NOT reach prod. Delivering needs a
c8c1d29-based branch with only these commits — no urgency while the routing is
still closed.

Refs R-STATE-03, R-ENV-02, R-IDP-05.

Co-Authored-By: Claude Opus 5 <[email protected]>

clusters/base/cluster-vars.yaml

@@ -212,6 +212,28 @@ data:
   VELERO_BACKUP_SCHEDULE: "0 3 * * *"        # cron; overlays may differ
   VELERO_RETENTION: "168h"                   # dev short | prod long
 
+  # BACKUP TENANCY — the two knobs that keep two clusters sharing ONE MinIO from destroying each
+  # other's backups. Added 2026-09-05 when the operator ruled prod uses the SAME endpoint as dev.
+  #
+  # Sharing an endpoint is fine. Sharing a PATH is not, and nothing here was per-environment before:
+  #
+  #   VELERO  — bucket `velero`, no prefix, and BOTH clusters run schedules named `daily` and
+  #             `daily-resources-only`. Each cluster's Velero SYNCS backups it finds in the BSL into
+  #             itself as Backup CRs and GARBAGE-COLLECTS them when their TTL expires. Prod would
+  #             therefore adopt dev's backups and delete them on schedule.
+  #   CNPG    — destinationPath `s3://cnpg` with CNPG appending serverName, which defaults to the
+  #             CLUSTER NAME. Both environments have `keycloak-db`, `nextcloud-db`, `semaphore-db`,
+  #             so prod's Postgres would archive WAL into the exact prefix dev's does. Two servers
+  #             interleaving WAL into one Barman stream CORRUPTS THE CHAIN and destroys PITR — and
+  #             dev's DR restore is PROVEN (R-STATE-03). This is the worst of the two.
+  #
+  # THE BASE VALUES ARE DEV'S CURRENT LAYOUT ON PURPOSE, and must stay that way: dev's existing
+  # backups live at the bucket root / at `s3://cnpg`. Giving dev a prefix would ORPHAN the very
+  # backups its proven restore depends on — the same reason dev's EXTERNALDNS_TXT_OWNER_ID stays
+  # `default`. Prod, which has no history to preserve, takes the namespaced paths.
+  VELERO_BACKUP_PREFIX: ""                   # dev: bucket root (existing layout) | prod: "prod"
+  CNPG_BACKUP_PATH: "s3://cnpg"              # dev: bucket root (existing layout) | prod: "s3://cnpg/prod"
+
   # --- placement ---
   PLATFORM_NODE_SELECTOR_KEY: "kubernetes.io/os"   # base no-op selector; prod may pin roles
   PLATFORM_NODE_SELECTOR_VALUE: "linux"