[Docs] Document DeepSeek V4 pricing schedules

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​Opened on behalf of @taltas. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Documents the separate preview-weight and 0813 model IDs exposed by DeepSeek, OpenCode Go, Fireworks AI, and Baseten.
• Explains DeepSeek's peak/off-peak schedule taking effect at 16:00 UTC on August 16, 2026 and lists exact V4 Pro and V4 Flash peak rates.
• Lists OpenCode Go, Baseten, and Fireworks prices independently, including the different cached-input rates for each 0813 host.
• Clarifies that Zoo Code uses peak prices for static first-party cost estimates because off-peak rates vary by time of day.

Why this change was made

DeepSeek changed its pricing after the original provider documentation was written, while hosted providers publish different prices and separate IDs for the preview and 0813 checkpoints. Reviewers and users need the effective date and route-specific costs in one place.

Impact

Users can compare DeepSeek V4 routes without assuming the same checkpoint or price applies across first-party, subscription, and hosted-provider APIs.

Related PRs

• Extension: [Fix] DeepSeek V4 costs are underestimated after pricing changes Zoo-Code#1237

Screenshots

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Addressed in ab2d4f4 and 1aead6b: the guide now distinguishes first-party 0813 routes from self-hosted preview weights, lists exact provider IDs/versions, and warns about DeepSeek's planned significant price increase. The draft PR metadata and screenshots were refreshed to the final rendered state.