Replace vector-archiver with logarchiver (#308)

## Why

The Vector archiver leg wrote gzip NDJSON to S3 with no index or encryption. logarchiver replaces it with a Go service that seals raw logs to S3 as zstd + OpenPGP objects and indexes each object in ClickHouse (`logs.archive_index`), acking JetStream only after the object is stored and indexed.

## Changes

- Add logarchiver Deployment (`git.unkin.net/unkin/logarchiver:v0.1.0`), ConfigMap, and dedicated ServiceAccount, reusing the archiver's NATS (`log-consumer` / durable `archiver` / `ARCHIVE_SUBJECTS=logs.k8s.vault.>`), S3 (`logs-archive-s3`), ClickHouse (`clickhouse-credentials`) and `vault-ca` wiring.
- Encrypts to the `logarchive` gpg public key, fetched from the gpg engine via k8s auth (role `logging_logarchiver`, projected vault-audience token). `ack_wait` (5m) > batch `max_age` (2m) so messages aren't redelivered mid-batch.
- Add `logs.archive_index` DDL to the clickhouse-schema bootstrap Job (no TTL — outlives `logs.raw`).
- Remove the vector-archiver Helm release, values and pipeline ConfigMap.

Cross-repo: apply **terraform-vault #106** (gpg key + role/policy) before this syncs, or the pod can't fetch the public key. Sequencing: apply after #306 (already merged).

https://claude.ai/code/session_015ur3i7D2azsMAWTSVABApv
---------

Co-authored-by: benvin <neotheo@gmail.com>
Reviewed-on: #308
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/logging/kustomization.yaml

@@ -12,6 +12,9 @@ resources:
   - cephrgw.yaml
   - gateway.yaml
   - httproute.yaml
+  - serviceaccount_logarchiver.yaml
+  - configmap_logarchiver.yaml
+  - deployment_logarchiver.yaml
 
 # Vector pipelines are the single source of truth (also validated by
 # `vector test` in CI). Mounted into each tier via `existingConfigMaps`.
@@ -44,8 +47,3 @@ configMapGenerator:
       - vm-ingest.yaml=vector/vm-ingest.yaml
     options:
       disableNameSuffixHash: true
-  - name: vector-archiver-config
-    files:
-      - archiver.yaml=vector/archiver.yaml
-    options:
-      disableNameSuffixHash: true