8.0 line: CVE-2026-84445 (gRPC-Go DoS) unresolved on stable-8.0 and v8.0.8 — needs a grpc bump

## Request

Bump `google.golang.org/grpc` on `stable-8.0` to at least **v1.83.2** (matching `master`, `stable-8.1`, and `stable-8.2`), then cut an **8.0.9** patch release.

## Why

Our Trivy gate in [owncloud-docker/ocis](https://github.com/owncloud-docker/ocis) scans the `ocis` binary inside the image it just built. [Run 34955346272](https://github.com/owncloud-docker/ocis/actions/runs/34955346272) (2026-09-15) flags one advisory on the 8.0 line:

| Advisory | Dependency | v8.0.8 (released) | Fixed in | `stable-8.0` today |
| --- | --- | --- | --- | --- |
| CVE-2026-84445 (HIGH) | `google.golang.org/grpc` | v1.83.1 | 1.82.2, 1.83.2, or 1.85.0-dev | **v1.83.1 ❌** |

- CVE-2026-84445 — gRPC-Go xDS servers: Denial of Service (DoS) via crash due to missing validation. https://avd.aquasec.com/nvd/cve-2026-84445

Versions above were read directly from `go.mod` at the respective ref, not inferred.

## Unlike #12810 and #12903, this is not just a release-cadence gap

For the 8.1 and 8.2 lines, the fix for this same CVE already landed on the branch and only needs a release tag (see #12810, #12903). **`stable-8.0` itself is still short of the fix** — it's on grpc v1.83.1, which doesn't satisfy any of the three fixed-version options (1.82.2 / 1.83.2 / 1.85.0-dev). `master`, `stable-8.1`, and `stable-8.2` are all already on v1.83.2, so this should just be catching `stable-8.0` up to the same version.

## Downstream impact

I maintain the container images in [owncloud-docker/ocis](https://github.com/owncloud-docker/ocis). Our Trivy gate scans the built `ocis` binary, so until this is fixed we're carrying it as a suppression in `v8/8.0/.trivyignore` to keep the 8.0 image publishing — exactly the kind of suppression we'd rather not ship.

## If 8.0 is not a maintained line

If the intent is that 8.0 users move to a newer line rather than receive patches, please just say so and close this — we'd then retire the `8.0` image tag.

Check go.mod on the stable-8.0 branch and compare its google.golang.org/grpc version with v1.83.2 on the other branches. Update the dependency to a fixed version, follow the project’s 8.0 patch-release process to cut 8.0.9, and verify that the downstream Trivy scan no longer reports CVE-2026-84445.

Written by the indexing model from the issue text.