fix(cilium): rebuild image multi-arch and pin tag to 1.19.3

The previous image digest in values.yaml pointed at a single-arch
linux/arm64 manifest because 'make image' was run from an arm64 host
with the default buildx platform. Cozystack targets amd64 (Talos build
output, E2E runners, most real-world clusters) and also arm64 for
hybrid fleets, so Helm install would fail on amd64 nodes with 'no
matching manifest for linux/amd64 in the manifest list entries'
whenever somebody installed directly from this commit between merge
and the next release-tag CI rebuild.

Fix: rebuilt the image locally with
PLATFORM='linux/amd64,linux/arm64' make image from a buildx
docker-container driver, pushed the multi-arch manifest, and
refreshed values.yaml with:

- digest of the new multi-arch manifest list (verified via
  'docker manifest inspect': amd64 sha256:e1977323..., arm64
  sha256:8f5ab529...).
- tag bumped from 'latest' (emitted by the common-envs.mk settag
  macro on a non-tagged checkout) to '1.19.3', matching the
  established convention in every other packages/system/*/values.yaml
  so reviewers and incident response have a human-readable version
  anchor independent of digest chasing.

The Makefile is left untouched so the CI builder (which only uses the
default docker driver) keeps building single-arch for whatever
architecture it runs on; multi-arch is a responsibility of the
release-tag pipeline or an explicit local rebuild.

Assisted-By: Claude <noreply@anthropic.com>
Signed-off-by: Aleksei Sviridkin <f@lex.la>

packages/system/cilium/values.yaml

@@ -15,8 +15,8 @@ cilium:
     mode: "kubernetes"
   image:
     repository: ghcr.io/cozystack/cozystack/cilium
-    tag: latest
-    digest: "sha256:8f5ab52982fc848ee098ff89919e3528aa8f3a553b82106a25149dcd0b87ea7e"
+    tag: 1.19.3
+    digest: "sha256:700f06f4803a838a8e830be5ace4650e3ad82bdefabfb2f4d110368d307a5efb"
   envoy:
     enabled: false
   rollOutCiliumPods: true