更新知识库文档：补充嵌入模型配置提示与维度自动检测说明

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Generated automatically by astrbot-docs-agent-server.

• Upstream PR: fix: cannot automatically get embedding dim when create embedding provider AstrBot#5442
• Trigger: PR merged

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AI change summary:

• 更新 zh/use/knowledge-base.md 与 en/use/knowledge-base.md。
• 补充 OpenAI Embedding API Base URL 配置说明，明确自动补全 /v1 后缀逻辑。
• 补充 Gemini Embedding API Base URL 配置建议，说明无需手动添加 /v1beta。
• 新增创建嵌入模型提供商时自动检测向量维度的说明及故障排查提示。
• i18n：中英文文档均已同步更新。

Please review manually before merging.

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• This output is generated by AstrBot-Doc-Agent for review only.
• It does not represent the final documentation form.

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Checked 1 published document(s) in 1 knowledge base(s). No updates required.

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