`visualize-timeseries` crashes with OOM (exit code 137) in headless/Kubernetes environments

[Hackshaven]

Describe the bug
Running zyra visualize-timeseries on even a tiny CSV inside a Kubernetes pod causes the container to terminate with exit code 137. kubectl describe pod shows OOMKilled.

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Steps to reproduce

1. Deploy Zyra in Kubernetes with ~8 GiB memory limit.
2. Run:

   zyra visualize-timeseries \
     --input downloads/airtravel.csv \
     --x Month \
     --y 1958 \
     --output outputs/airtravel.png

3. Pod crashes with OOMKilled.

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Expected behavior
Plot should render successfully with modest memory usage.

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Root cause analysis

• src/zyra/visualization/timeseries_manager.py imports matplotlib.pyplot without forcing a non-interactive backend.
• In headless pods, Matplotlib defaults to interactive backends (TkAgg, Qt5Agg), which misbehave and leak memory.
• Figures are not always closed (plt.close(fig) missing), leading to accumulation.

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Proposed fix

• Add:

  import matplotlib
  matplotlib.use("Agg")

  before importing pyplot.
• Ensure plt.close(fig) after save to free memory.

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Environment

• Zyra main branch
• Kubernetes pod with memory limit 8 GiB
• MPLBACKEND unset