feat: add litellm to new aitooling ArgoCD project (#94)

Deploys LiteLLM proxy with CNPG PostgreSQL (3-instance HA), PgBouncer
pooler, and Redis cache. Introduces a dedicated aitooling AppProject and
ApplicationSet to keep AI tooling services separate from platform infra.

Reviewed-on: #94

apps/base/litellm/vaultauth.yaml

@@ -0,0 +1,18 @@
+---
+apiVersion: secrets.hashicorp.com/v1beta1
+kind: VaultAuth
+metadata:
+  name: default
+  namespace: litellm
+spec:
+  allowedNamespaces:
+    - litellm
+  kubernetes:
+    audiences:
+      - vault
+    role: default
+    serviceAccount: default
+    tokenExpirationSeconds: 600
+  method: kubernetes
+  mount: k8s/au/syd1
+  vaultConnectionRef: vso-system/default