feat(model_prices): add zai/glm-5.3-flash pricing

[LeonxLJX]

Fixes #38608

Add zai/glm-5.3-flash pricing to model_prices_and_context_window.json and litellm/model_prices_and_context_window_backup.json.

Pricing per https://docs.z.ai/guides/overview/pricing:

• Input: $0.15 / 1M tokens
• Output: $0.50 / 1M tokens
• Cached input: $0.03 / 1M tokens
• Context window: 1M tokens

[CLAassistant]

All committers have signed the CLA.

[greptile-apps]

Greptile Summary

Adds pricing, context-window limits, and capability metadata for Z.AI's glm-5.3-flash model.

• Registers input, output, and cached-input token costs.
• Declares the model's context limits and supported chat capabilities.
• Keeps the primary and backup model metadata catalogs synchronized.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The two synchronized metadata entries register the requested model using pricing and context limits consistent with the stated provider information, and the existing Z.AI model-prefix path can resolve the new key.

Important Files Changed

Filename	Overview
model_prices_and_context_window.json	Adds a reachable Z.AI model entry whose documented pricing and context-window values match the PR description.
litellm/model_prices_and_context_window_backup.json	Mirrors the new model metadata entry exactly in the backup catalog.

_{Reviews (1): Last reviewed commit: "feat(model_prices): add zai/glm-5.3-flas..." | Re-trigger Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing LeonxLJX:add-glm-5.3-flash-pricing (d6bf3bb) with main (e55dbaf)}

[devin-ai-integration]

Superseded by the rolling registry PR #38560, which absorbs this entry field-for-field (verified against https://docs.z.ai/guides/overview/pricing and the GLM-5.3-Flash model page) and additionally sets supports_vision: true per the documented image/video input modality. Closing to keep a single open registry PR.