fix(infra): correct OTel collector image tag (#59)

## Summary
`otel/opentelemetry-collector-contrib:0.115.0` doesn't exist — release 0.115 was published as `0.115.1` only. Same memory-not-Docker-Hub mistake as Jaeger in #58.

```
Error response from daemon: failed to resolve reference
"docker.io/otel/opentelemetry-collector-contrib:0.115.0": not found
```

Pin to `0.150.1` (latest stable). The collector's stable-feature backward-compat covers our `otel-collector.yaml` (otlp receiver, batch processor, debug exporter, otlp/jaeger exporter) — no config change needed.

Postgres `17.2-alpine`, Redis `7.4-alpine`, pgweb `0.16.2` were verified against Docker Hub at the same time; they're all correct.

## Test plan
- [ ] `cd infra/local && docker compose -f dev.compose.yml up -d` — all 3 core services pull and start healthy.
- [ ] `--profile observability up -d` adds Jaeger 1.76.0 (after #58).
- [ ] `--profile dbtools up -d` adds pgweb 0.16.2.
- [ ] `docker compose ps` shows everything healthy.

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #59

infra/local/dev.compose.yml

@@ -80,7 +80,7 @@ services:
       retries: 5
 
   otel-collector:
-    image: otel/opentelemetry-collector-contrib:0.115.0
+    image: otel/opentelemetry-collector-contrib:0.150.1
     container_name: apf-portal-otel-collector
     restart: unless-stopped
     command: ['--config=/etc/otel-collector.yaml']