[FEAT][Helm] Support setting env for router

[treydock]

Allow setting custom environment variables for the router. Right now we run the router as a specific UID and have to map the username like so:

        env:
          - name: USER
            value: feithosu
          - name: LOGNAME
            value: feithosu

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[gemini-code-assist]

Code Review

This pull request enables the configuration of environment variables for the router component by adding an env field to the routerSpec. Changes include updating the deployment template to inject these variables, defining the field in the JSON schema, and providing a default empty list in values.yaml. Feedback suggests improving the JSON schema by explicitly defining the expected structure of the environment variable objects (e.g., name, value, valueFrom) to provide better validation for users.

[gemini-code-assist]

While consistent with other env definitions in this schema, it is generally a best practice to define the expected structure of the array items (e.g., objects with name, value, and valueFrom properties). This provides better validation for users when they provide custom environment variables.

[treydock]

This would limit the types of environment variables, as it could be coming from secret ref or configmap ref and not strictly name/value. Add all the types seems overly burdensome to this project.

[ruizhang0101]

LGTM