catalog: two tiny services, so the loop can be exercised on a full cluster

The three existing entries are sized like real products: `elasticsearch` small
asks for 1Gi and medium for 4Gi across three replicas. On this cluster that is
a request that never schedules, so provisioning them proves something about the
node and nothing about svcforge.

  podinfo  16Mi/10m  — one small Go binary, no dependencies, no PVC
  nginx    32Mi/10m  — recognisable, still small

Both are addressed as `oci://`, which is load-bearing rather than cosmetic. An
OCI chart is pulled by reference with no `helm repo add` first. The three
existing entries name `bitnamilegacy/<chart>`, a classic repo alias that
nothing in the worker image configures — so as written they cannot resolve at
provision time. OCI is the form that works from a bare container, and it is why
the e2e test already provisions podinfo.

Chart versions were resolved against the real registries before committing
(podinfo 6.7.1, nginx 25.0.14 / app 1.31.3) rather than guessed, since a wrong
version fails only at provision time.

Also updates the CLI ServiceType enum, the catalog test's expected set, and the
service list in the OpenAPI description.

services/api/main.py

@@ -91,7 +91,9 @@ async def lifespan(app: FastAPI) -> AsyncIterator[None]:
 # to create_app rather than in a README because /docs is what someone integrating actually
 # reads, and a README in this repo is not something they have.
 API_DESCRIPTION = """
-Provision managed service instances (Elasticsearch, Redis, Postgres) into Kubernetes.
+Provision managed service instances into Kubernetes. The catalog offers Elasticsearch,
+Redis and Postgres, plus two deliberately tiny entries — `podinfo` and `nginx` — for
+exercising the platform where there is no room for the real thing.
 
 ## Authentication
 

services/api/models.py

@@ -32,7 +32,8 @@ class CreateInstanceRequest(BaseModel):
     service_type: str = Field(
         min_length=1,
         description=(
-            "A service type in the catalog, e.g. `elasticsearch`, `redis`, `postgres`. "
+            "A service type in the catalog, e.g. `elasticsearch`, `redis`, `postgres`, "
+            "`podinfo`, `nginx`. "
             "Unknown values return 404."
         ),
     )

services/cli/main.py

@@ -31,6 +31,9 @@ class ServiceType(StrEnum):
     ELASTICSEARCH = "elasticsearch"
     REDIS = "redis"
     POSTGRES = "postgres"
+    # Small enough to provision on a cluster with no spare memory; see catalog.yaml.
+    PODINFO = "podinfo"
+    NGINX = "nginx"
 
 
 class Size(StrEnum):