feat(vision-proxy): add configurable request timeout

[esnho]

Summary

Adds an optional Request timeout (ms) field to the Vision Proxy
settings panel so users can increase the HTTP timeout for slow vision
API endpoints. Previously the timeout was hardcoded at 30 seconds.

Behavior

Input	Result
Empty / not set	Falls back to the existing default (30 000 ms)
Any positive number	Used as the fetch timeout for vision requests
Zero, negative, or non-finite	Treated as unset → falls back to default
No upper cap	No arbitrary limit — users decide what works for their endpoint

Files changed

• src/provider/vision/types.ts — add optional timeoutMs to
  VisionProxyConfig
• src/provider/vision/sources/endpoint/config.ts — add
  normalizeTimeoutMs() (validates > 0, no cap)
• src/provider/vision/protocols/client.ts — use
  config.timeoutMs ?? DEFAULT_TIMEOUT_MS
• src/provider/vision/ui/html.ts — add <input type="number"> field
  with label + hint
• src/provider/vision/ui/script.ts — wire parsePositiveNumber(),
  applyState, collectConfig for the new field
• src/i18n.ts — add field.timeoutMs / hint.timeoutMs strings for
  both en and zh dictionaries

Screenshots

Translation review requested

The Chinese (zh) translations for the new strings were written with the
help of an AI assistant. A native speaker should review them:

// i18n.ts — zh dictionary
'vision.panel.field.timeoutMs': '请求超时 (毫秒)',
'vision.panel.hint.timeoutMs': '留空使用默认 30 秒。值必须大于 0。',

Corresponding English:

'vision.panel.field.timeoutMs': 'Request timeout (ms)',
'vision.panel.hint.timeoutMs': 'Leave empty for the default 30 seconds. Must be greater than 0.',

🙏 Please flag anything that sounds unnatural or could be improved.

[Vizards]

Thanks — a configurable timeout is useful here. Before merging, could you add an explicit maximum for timeoutMs?

I suggest exactly 2_147_483_647 ms (2147483647) and enforcing it both in the backend normalization and on the HTML input with max="2147483647".

Node's setTimeout() treats any delay larger than 2147483647 as 1 ms. As written, an oversized user value would therefore produce an almost immediate timeout, which is the opposite of the intended behavior. The proposed maximum is about 24.86 days, so it should not restrict any realistic vision request.

It would also be good to accept integers only (step="1" and/or backend integer normalization), since Node truncates non-integer delays.

Reference: https://nodejs.org/api/timers.html#settimeoutcallback-delay-args