feat: OpenMesh 基础平台与 MD/PDF 转换技能

- 后端: coworker 智能体框架, WS API, 文件上传, 附件处理
- 前端: Open WebUI, 文件全量走 upload API (含 MD/TXT/JSON 等文本类)
- 技能: md-to-office (pandoc + wkhtmltopdf)
- 修复: 上传文件路径丢失, Agent 搜索浪费, 输出文件跑到 uploads/
- 打包: PyInstaller one-dir, 预打包 pandoc/wkhtmltopdf/chromium

coworker/web/providers.py

@@ -0,0 +1,128 @@
+"""Web search providers — a keyless default + pluggable third-party services.
+
+`duckduckgo` works with no API key (our "starting version of our own"). `tavily` and `brave`
+give better results but need a key (configured via the SecretStore / env). All providers
+return a uniform `list[SearchResult]`; the heavy client libs are lazy-imported.
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Optional
+
+_TIMEOUT = 20.0
+
+
+@dataclass
+class SearchResult:
+    title: str
+    url: str
+    snippet: str
+
+    def to_dict(self) -> dict:
+        return {"title": self.title, "url": self.url, "snippet": self.snippet}
+
+
+class WebSearchProvider(ABC):
+    name: str = "base"
+    requires_key: bool = False
+
+    @abstractmethod
+    def search(self, query: str, max_results: int = 5) -> list[SearchResult]: ...
+
+
+class DuckDuckGoProvider(WebSearchProvider):
+    """Keyless default via the `ddgs` library."""
+
+    name = "duckduckgo"
+    requires_key = False
+
+    def search(self, query: str, max_results: int = 5) -> list[SearchResult]:
+        from ddgs import DDGS
+
+        rows = DDGS().text(query, max_results=max_results) or []
+        return [
+            SearchResult(
+                title=r.get("title", ""),
+                url=r.get("href", "") or r.get("url", ""),
+                snippet=r.get("body", "") or r.get("snippet", ""),
+            )
+            for r in rows
+        ]
+
+
+class TavilyProvider(WebSearchProvider):
+    name = "tavily"
+    requires_key = True
+
+    def __init__(self, api_key: str) -> None:
+        self.api_key = api_key
+
+    def search(self, query: str, max_results: int = 5) -> list[SearchResult]:
+        import httpx
+
+        resp = httpx.post(
+            "https://api.tavily.com/search",
+            json={"api_key": self.api_key, "query": query, "max_results": max_results},
+            timeout=_TIMEOUT,
+        )
+        data = resp.json()
+        return [
+            SearchResult(
+                title=r.get("title", ""),
+                url=r.get("url", ""),
+                snippet=r.get("content", ""),
+            )
+            for r in data.get("results", [])
+        ]
+
+
+class BraveProvider(WebSearchProvider):
+    name = "brave"
+    requires_key = True
+
+    def __init__(self, api_key: str) -> None:
+        self.api_key = api_key
+
+    def search(self, query: str, max_results: int = 5) -> list[SearchResult]:
+        import httpx
+
+        resp = httpx.get(
+            "https://api.search.brave.com/res/v1/web/search",
+            headers={
+                "X-Subscription-Token": self.api_key,
+                "Accept": "application/json",
+            },
+            params={"q": query, "count": max_results},
+            timeout=_TIMEOUT,
+        )
+        data = resp.json()
+        return [
+            SearchResult(
+                title=r.get("title", ""),
+                url=r.get("url", ""),
+                snippet=r.get("description", ""),
+            )
+            for r in (data.get("web", {}) or {}).get("results", [])
+        ]
+
+
+_PROVIDERS = {
+    "duckduckgo": DuckDuckGoProvider,
+    "tavily": TavilyProvider,
+    "brave": BraveProvider,
+}
+
+
+def build_provider(name: str, api_key: Optional[str] = None) -> WebSearchProvider:
+    cls = _PROVIDERS.get(name, DuckDuckGoProvider)
+    if cls.requires_key:
+        if not api_key:
+            raise ValueError(f"web search provider '{name}' needs an API key")
+        return cls(api_key)  # type: ignore[call-arg]
+    return cls()  # type: ignore[call-arg]
+
+
+def provider_names() -> list[str]:
+    return list(_PROVIDERS)