fix(mem): correct GPU memory accounting (host vs container) and memory limits accordingly

[loiht2]

• Fixes incorrect GPU memory reporting inside the container vs. on the host (as shown by nvidia-smi).
• Enforces GPU memory limits using the corrected container-visible memory, preventing incorrect OOM enforcement.

GPU Memory Usage

In container

Command: nvidia-smi

Command: nvidia-smi -a

    FB Memory Usage
        Total                             : 3072 MiB
        Reserved                          : 274 MiB
        Used                              : 2584 MiB
        Free                              : 488 MiB

On host

Command: nvidia-smi

Command: nvidia-smi -a

    FB Memory Usage
        Total                             : 32768 MiB
        Reserved                          : 274 MiB
        Used                              : 2588 MiB
        Free                              : 29907 MiB

GPU Memory Limit Enforcement (OOM scenario)

I run the same pod, which requires ~2588 MiB GPU memory. However, in this test, the ResourceClaim requests only 2GiB (2048 MiB) GPU memory, so the pod hits GPU OOM.

Pod log showing the OOM:

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This pull-request has been approved by: loiht2
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