Add external knowledge base support for HTTP-based RAG retrieval

[Copilot]

概述 / Overview

Extends RAG capabilities with external knowledge bases via HTTP API. Built-in knowledge bases had limited retrieval quality; external KBs allow integration with superior third-party retrieval services (e.g., Dify-compatible APIs).

实现细节 / Implementation Details

Backend Architecture:

• Abstract KnowledgeBaseInterface for polymorphic KB handling (internal/external)
• ExternalKnowledgeBase implementation with async HTTP client, Bearer auth support
• ExternalKnowledgeBase persistence table (uuid, name, api_url, api_key, top_k)
• Full CRUD endpoints at /api/v1/knowledge/external-bases
• RAGManager loads both KB types; pipelines retrieve from mixed sources seamlessly

Frontend UI:

• Tab navigation: Built-in | External (styled to match plugins page design)
• External KB card list with create/edit dialog
• Form fields: name, description, API URL, API key (optional), top_k
• HTTP client methods for external KB operations
• i18n: EN, ZH-Hans, ZH-Hant, JA

API Contract:

POST {api_url}
Authorization: Bearer {api_key}
Content-Type: application/json

{"query": "text", "top_k": 5}

Response: {"records": [{"content": "...", "score": 0.95, "title": "...", "metadata": {}}]}

Backward Compatibility:

• Existing internal KBs unchanged
• Pipeline knowledge-bases array field already supported
• Legacy single knowledge-base string still works
• Auto-creates tables on startup

检查清单 / Checklist

PR 作者完成 / For PR author

• 阅读仓库贡献指引了吗？ / Have you read the contribution guide?
• 与项目所有者沟通过了吗？ / Have you communicated with the project maintainer?
• 我确定已自行测试所作的更改，确保功能符合预期。 / I have tested the changes and ensured they work as expected.

项目维护者完成 / For project maintainer

• 相关 issues 链接了吗？ / Have you linked the related issues?
• 配置项写好了吗？迁移写好了吗？生效了吗？ / Have you written the configuration items? Have you written the migration? Has it taken effect?
• 依赖加到 pyproject.toml 和 core/bootutils/deps.py 了吗 / Have you added the dependencies to pyproject.toml and core/bootutils/deps.py?
• 文档编写了吗？ / Have you written the documentation?

Original prompt

我们内置的知识库（RAG）检索算法比较简单，效果质量并不好；我们希望能通过“外部知识库”来扩展能力，外部知识库即通过http来检索文档，只需要使用到检索接口；我们假设外部知识库会提供与：https://docs.dify.ai/zh-hans/guides/knowledge-base/api-documentation/external-knowledge-api-documentation 文档定义的格式一样的接口，请你设计支持外部知识库；

请在知识库页面左上角加一个tab list，可以参考插件页的用法；分为两个tab：内置、外部知识库；当切换到 外部知识库时，显示外部知识库的列表，最左上角的卡片是 添加卡片 （可以参考其他页面的组件），点击添加卡片即弹出对话框，供用户输入外部知识库的地址；

后端中，请你做好抽象，在内置知识库和外部知识库上方加一个抽象层？在流水线配置的选择知识库时，需要支持同时选择多个内置知识库或外部知识库；流水线检索时，内部知识库就是使用内部的rag逻辑，外部知识库则直接访问外部知识库的检索api；

注意：上方那个文档仅供参考，请根据 LangBot 内部所需的字段和具体情况来对外部知识库的接口做出定义；

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[RockChinQ]

@copilot 知识库页面的左上角tab list样式很难看，请参考插件页面的那个tab list样式实现

[Copilot]

@copilot 知识库页面的左上角tab list样式很难看，请参考插件页面的那个tab list样式实现

Updated the tab list styling to match the plugins page. Changes in commit abe9795:

• Added flex container with justify-between and px-[0.8rem] padding
• Applied shadow-md, py-5, and bg-[#f0f0f0] dark:bg-[#2a2a2e] to TabsList
• Added px-6 py-4 cursor-pointer to each TabsTrigger

The knowledge base tabs now have the same visual style as the plugins page tabs.