feat: add Gonka Broker as a model provider

[iamoeco]

Describe Your Changes

Adds Gonka Broker as a built-in remote model provider.

Gonka Broker is an OpenAI-compatible API that serves open-source models (MiniMax, Kimi and others)
running on the decentralized Gonka network. It follows the same pattern as the existing
gateway providers (OpenRouter): the provider ships with models: [] and Jan fetches the
available models live from {base_url}/models, so there is no hardcoded model list to
maintain and no per-model PRs.

Changes:

• web-app/src/constants/providers.ts — provider entry (base_url: https://proxy.gonkabroker.com/v1, API-key setting, models: [])
• web-app/src/constants/models.ts — provider capability flags (auto-fetch, completion, streaming, JSON, images, tool calls, n)
• web-app/src/lib/providerCaps.ts — sampler capabilities (mirrors the OpenRouter gateway profile)
• web-app/src/lib/utils.ts — getProviderLogo + getProviderTitle entries
• web-app/public/images/model-provider/gonkabroker.svg — provider logo
• docs/src/pages/docs/desktop/remote-models/gonkabroker.mdx — integration guide
• docs/src/pages/docs/desktop/remote-models/_meta.json, docs/src/pages/docs/desktop/manage-models.mdx, docs/_redirects — docs wiring

Verified:

• tsc -b typecheck and eslint pass on the web-app workspace
• Provider validates and lists models against the live endpoint with a real key; inference works (streaming + non-streaming) on MiniMaxAI/MiniMax-M2.7 and moonshotai/Kimi-K2.6

Fixes Issues

• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[iamoeco]

Hi @Vanalite — gentle bump 🙏 CI is in "action required" (first-contributor gate). Could a maintainer hit "Approve and run"? The PR mirrors the predefined cloud-provider pattern (like your NVIDIA NIM / MiniMax additions) — auto-fetches models from /v1/models, no CLA/DCO — and I've verified it end-to-end against our live endpoint. Thanks!