fix: force Bocha search API requests to use gzip/deflate encoding to avoid aiohttp 3.12+ brotli decoding errors.

[MagicSun7940]

Fixes #7654

当 aiohttp >= 3.12 时，Bocha 搜索 API 返回 brotli 压缩格式的响应，而 aiohttp 3.12+ 在处理 brotli 解压时存在 bug，导致所有 Bocha 搜索请求失败，报错 Can not decode content-encoding: br。

Modifications / 改动点

• 修改 astrbot/core/tools/web_search_tools.py 中的 _bocha_search() 函数，在请求头中添加 Accept-Encoding: gzip, deflate，禁止服务器返回 brotli 格式响应，从根本上规避 aiohttp 的兼容性问题。

• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

修复前报错：
aiohttp.http_exceptions.ContentEncodingError: 400, message:
Can not decode content-encoding: br
aiohttp.client_exceptions.ClientPayloadError: 400, message:
Can not decode content-encoding: br

修复后（将 aiohttp 降至 3.11.18 验证逻辑正确，加上此 header 后 aiohttp 3.13.x 下同样正常）：
Tool web_search_bocha 正常返回搜索结果。

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Checklist / 检查清单

• 😊 If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
  / 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。

• 👀 My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  / 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。

• 🤓 I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
  / 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到 requirements.txt 和 pyproject.toml 文件相应位置。

• 😮 My changes do not introduce malicious code.
  / 我的更改没有引入恶意代码。

Summary by Sourcery

Bug Fixes:

• Force Bocha search API requests to use gzip/deflate encoding to avoid aiohttp 3.12+ brotli decoding errors.

[sourcery-ai]

Hey - I've left some high level feedback:

• Consider adding a brief inline comment (with an aiohttp issue/PR reference if available) explaining why Accept-Encoding is restricted here, so future maintainers understand this is a workaround for a specific brotli handling bug rather than an arbitrary header choice.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider adding a brief inline comment (with an aiohttp issue/PR reference if available) explaining why `Accept-Encoding` is restricted here, so future maintainers understand this is a workaround for a specific brotli handling bug rather than an arbitrary header choice.

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[gemini-code-assist]

Code Review

This pull request adds an Accept-Encoding header to the _bocha_search function to explicitly support gzip and deflate compression. The reviewer suggested adding a code comment to document that this change avoids a known brotli decompression issue in aiohttp 3.12+ and recommended applying similar changes to other search utility functions like _tavily_search and _brave_search.

[gemini-code-assist]

由于 aiohttp 3.12+ 的 brotli 解压问题是库层面的通用问题，建议检查并考虑在本项目中其他使用 aiohttp 进行网络请求的函数（如 _tavily_search, _brave_search 等）中也显式指定 Accept-Encoding，以防止这些服务在未来启用 brotli 压缩时导致类似的崩溃。此外，建议在代码中添加注释说明此 Header 的作用，以便后续维护。

Suggested change

	"Accept-Encoding": "gzip, deflate",
	"Accept-Encoding": "gzip, deflate", # 规避 aiohttp 3.12+ brotli 解压 bug