fix: update dex to work with basehref

[jy4096]

Local Test

Numaflow Dex Server deployment

redirectURIs: 
  - https://localhost:8443/numaflow/login

Numaflow Server deployment

 - name: main
   image: quay.io/numaproj/numaflow:latest
   args:
   - "server"
   - "--base-href=/numaflow"

 - name: server-init
   image: quay.io/numaproj/numaflow:latest
   args:
   - "server-init"
   - "--base-href=/numaflow"

demo.mov