feat(home-assistant): grow ha-pg storage 20Gi -> 32Gi (REN-141)

One semantic line: spec.storage.size 20Gi -> 32Gi. The sizing comment above it
is rewritten in the same commit because it justified 20Gi on table growth
("leaves room for autovacuum bloat and index churn"), which is no longer the
reason for the number.

The reason is WAL headroom during an archiving stall. 20Gi left 6.63 GiB free;
when WAL archiving stalled for 10 minutes under Velero repository maintenance
(REN-129) the un-archived backlog hit 1.84 GiB, 28% of that free space. Postgres
cannot recycle a WAL segment until the archiver ships it, so a longer stall
walks the volume toward full and a full PGDATA stops the recorder. 32Gi takes
free space to ~18.6 GiB and the same backlog to 10% of headroom.

Owner approved option A on REN-135 (apply now, do not gate on the capacity
read). Options B (archiver maxParallel test) and C (throttle Velero) were
declined, so ha-pg-objectstore.yaml and Velero are untouched.

Verified by parsing the file before and after: with spec.storage.size masked,
the two documents are byte-identical as parsed objects. instances: 2,
storageClass: ceph-block, all 8 postgresql.parameters and resources are
unchanged.

NOT verified here: `ceph df` for the replicapool pool. This runtime has no
kubectl and no Ceph read path — see the PR body.

Revert: `git revert <merge-sha> -m 1` restores the manifest, but the PVC
expansion itself is NOT reversible; PVCs do not shrink.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Co-Authored-By: Paperclip <noreply@paperclip.ing>

kubernetes/apps/home-assistant/ha-pg-cluster.yaml

@@ -36,12 +36,22 @@ spec:
   imageName: ghcr.io/cloudnative-pg/postgresql:16
   storage:
     storageClass: ceph-block
-    # Sized for the migrated statistics plus 7 days of states at the current
-    # rate: statistics 10.8M rows + statistics_short_term 1.9M (~1.8 GB with
-    # indexes in Postgres) and ~18M states rows for the purge_keep_days:7 window
-    # (~4 GB). 20Gi leaves room for autovacuum bloat and index churn.
-    # ceph-block has allowVolumeExpansion: true, so this can grow in place.
-    size: 20Gi
+    # Sized for WAL headroom during an archiving stall, not for table growth.
+    # The data itself needs far less: migrated statistics 10.8M rows +
+    # statistics_short_term 1.9M (~1.8 GB with indexes in Postgres) and ~18M
+    # states rows for the purge_keep_days:7 window (~4 GB).
+    #
+    # 20Gi left only 6.63 GiB free, and that is the number that matters here.
+    # When WAL archiving stalled for 10 minutes while Velero ran repository
+    # maintenance (REN-129), the un-archived backlog reached 1.84 GiB — 28% of
+    # that free space. Postgres cannot recycle a WAL segment until the archiver
+    # has shipped it, so a longer stall walks the volume toward full, and a
+    # full PGDATA stops the recorder outright.
+    #
+    # 32Gi takes free space to ~18.6 GiB, which puts the same 1.84 GiB backlog
+    # at 10% of headroom rather than 28%. Approved by the owner on REN-135.
+    # ceph-block has allowVolumeExpansion: true, so this grows in place.
+    size: 32Gi
   plugins:
     - name: barman-cloud.cloudnative-pg.io
       isWALArchiver: true