Adds first-class support for configuring more than one custom
OpenAI-compatible provider (e.g. SiliconFlow, DeepSeek, local vLLM)
and switching the active one from the web console, addressing #2838.
Backend:
- config: new `custom_providers` (list) and `custom_active_provider`
fields, fully backward compatible with the legacy single
`open_ai_api_base`/`model` fields (used as fallback).
- models/custom_provider.py: centralized resolver
`resolve_custom_credentials()` returning (api_key, api_base, model),
with active-provider selection and graceful fallback.
- chat_gpt_bot.py wired to use the resolver.
- web_channel.py: `_provider_overview` expands `custom_providers` into
one card per provider (id `custom:<name>`, active flag, masked key);
new POST actions `set_custom_provider`, `delete_custom_provider`,
`set_active_custom_provider` with hermetic persistence + bridge reset.
Frontend:
- console.js: dedicated "Custom providers" section with add / edit /
delete / set-active actions, masked-key keep-existing handling, and
~20 new zh/en i18n strings.
- chat.html: custom provider modal.
Tests:
- tests/test_custom_provider.py (11) - resolver/config behavior.
- tests/test_custom_provider_handlers.py (18) - write-side handlers and
overview expansion, including duplicate-name rejection.
All 29 unit tests pass.
