feat: add Docker, Drone CI, and k8s deployment manifests

- Dockerfile for Python 3.12 FastAPI app
- Drone CI pipeline to build and push to internal registry
- Kubernetes manifests (Deployment, Service, Secret, Namespace)
- ArgoCD Application for GitOps deployment
- Kustomize base configuration

k8s/base/service.yaml

@@ -0,0 +1,15 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: invest-api
+  namespace: invest-api
+  labels:
+    app: invest-api
+spec:
+  type: ClusterIP
+  selector:
+    app: invest-api
+  ports:
+    - port: 8000
+      targetPort: 8000
+      protocol: TCP