[Observability] Deploy OpenTelemetry Collector and Parca/eBPF profiling backends

### Task Summary
Stand up the local deployment wiring that receives and stores telemetry, default-off and isolated from the application services.
- Add an OpenTelemetry Collector configuration and wire it into the single-node `docker-compose` stack.
- Add the Parca server configuration and the Parca eBPF agent for continuous profiling.
- Update the single-node `up.sh` and `.env` to start the observability backends.
- Add configuration-validation specs for the collector and Parca config.
- The application runs unchanged whether or not these services are started.
### Task Type
- [x] DevOps / Deployment / CI
- [ ] Refactor / Cleanup
- [ ] Testing / QA
- [ ] Documentation
- [ ] Performance
- [ ] Other
### Related
Part of #4070. Depends on #5368.