chore(deps): pin protobufjs to >=8.0.2 to clear 7 transitive advisories (#111)

## Summary

`protobufjs 8.0.0` / `8.0.1` ship 7 fresh advisories (4 high, 3 moderate) pulled in transitively as `@opentelemetry/exporter-trace-otlp-http → @opentelemetry/otlp-transformer → protobufjs`. `pnpm audit --audit-level=moderate` flags them, which blocks the `ci:audit` gate on every push.

Pins the package directly via `pnpm.overrides` — same shape we already use for `axios`, `brace-expansion`, `follow-redirects`, `ip-address`, `tmp`, `yaml`. Resolution lands on `protobufjs@8.2.0` (latest stable). The override is `protobufjs@<8.0.2: ">=8.0.2"` so it auto-yields the moment a non-vulnerable transitive lands and the override becomes a no-op — no need to remember to remove it.

## Advisories cleared

| ID                  | Severity | Issue                                                 |
| ------------------- | -------- | ----------------------------------------------------- |
| GHSA-66ff-xgx4-vchm | high     | code generation gadget                                |
| GHSA-75px-5xx7-5xc7 | high     | code generation gadget after prototype pollution      |
| GHSA-jvwf-75h9-cwgg | high     | process-wide DoS through unsafe option paths          |
| GHSA-685m-2w69-288q | high     | DoS through unbounded protobuf recursion              |
| GHSA-q6x5-8v7m-xcrf | moderate | overlong UTF-8 decoding                               |
| GHSA-2pr8-phx7-x9h3 | moderate | DoS from crafted field names in generated code        |
| GHSA-fx83-v9x8-x52w | moderate | prototype injection in generated message constructors |

## Test plan

- [x] `pnpm audit --audit-level=moderate` → **No known vulnerabilities found**
- [x] `pnpm nx test portal-bff` → 99/99 pass
- [x] `pnpm nx build portal-bff` → webpack compiled successfully
- [x] `pnpm install` resolves `protobufjs@8.2.0` (verified in lockfile)

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #111

package.json

@@ -37,6 +37,7 @@
       "brace-expansion@<5.0.5": ">=5.0.5",
       "follow-redirects@<1.16.0": ">=1.16.0",
       "ip-address@<10.1.1": ">=10.1.1",
+      "protobufjs@<8.0.2": ">=8.0.2",
       "tmp@<0.2.4": ">=0.2.4",
       "yaml@<2.8.3": ">=2.8.3"
     }