Build Tempo container from source (2.10.3) (#323)

## Summary
- Add `containers/tempo/Dockerfile` — two-stage Go build from forge mirror, modeled on loki
- Switch kustomization from upstream `grafana/tempo` to `registry.ops.eblu.me/blumeops/tempo`
- Bump Tempo 2.10.1 → 2.10.3

## Test plan
- [ ] Kick off container build via `mise run container-build-and-release tempo`
- [ ] Update kustomization `newTag` with built image tag
- [ ] Deploy from branch: `argocd app set tempo --revision local-tempo-container && argocd app sync tempo`
- [ ] Verify Tempo health: `curl tempo.ops.eblu.me/ready`
- [ ] Verify traces flowing in Grafana Tempo datasource

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #323

argocd/manifests/tempo/kustomization.yaml

@@ -11,7 +11,8 @@ resources:
 
 images:
   - name: grafana/tempo
-    newTag: "2.10.1"
+    newName: registry.ops.eblu.me/blumeops/tempo
+    newTag: "v2.10.3-49ce545"
 
 configMapGenerator:
   - name: tempo-config