Add proxy configuration to help rotate Baidu IPs

[Dux1007]

Summary

• allow the Baidu index client to accept default and per-request proxy overrides when fetching data
• expose proxy configuration through new environment variables and the API/front-end form so users can route traffic via another IP
• document proxy usage in the README to guide users on switching networks when blocked

Testing

• python -m compileall app start_app.py

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https://chatgpt.com/codex/tasks/task_e_68f31e417a34832f91a6fdef169bb3ff

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Import removed Pydantic validator decorator

The models module still imports and uses validator, but requirements.txt pins FastAPI ≥0.110 which installs Pydantic v2, where the top‑level validator symbol has been removed. Attempting to import this module will raise ImportError: cannot import name 'validator' from 'pydantic', preventing the API from starting. Switch to field_validator or import from pydantic.v1 so the validation code works under the dependencies declared here.

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