feat(ai): add DaoXE as a model provider

[seven7763]

What this PR does / why we need it?

Adds DaoXE as a selectable AI agent model provider. DaoXE is an
OpenAI-compatible multi-model LLM gateway (hundreds of models behind one API key) that
also serves Anthropic Messages on the same account, so it can back both OpenAI-type and
Claude-type agent flows in 1Panel.

Affiliation disclosure for transparency: I maintain this gateway, and this PR registers
it in the provider catalog the same way existing gateways (OpenRouter, DeepSeek, ...)
are registered.

Summary of your change

• agent/app/provider/catalog.go: new daoxe entry (Sort 57, next to OpenRouter) with
  openai-completions / openai-responses / openai-embeddings on
  https://api.daoxe.com/v1 (model discovery enabled — standard GET /v1/models) and an
  anthropic-messages config on https://api.daoxe.com (x-api-key default, bearer
  optional). Added to legacyModelPrefixes. No hardcoded model list: models are
  discovered at runtime, so the entry stays correct as the catalog behind it changes.
• frontend/src/utils/agent-provider-logo.ts: provider logo, inlined as an SVG data URI
  so no binary asset is added to the repo (happy to switch to a committed
  ai-providers/daoxe.svg if maintainers prefer the file convention).
• No verify.go / openclaw.go / agents special-cases needed: DaoXE is a keyed provider
  using the standard bearer-verification path (unlike ollama/llmman local runners).

Testing: go build / go vet / gofmt -l on agent/app/provider,
agent/app/service, agent/utils/terminal/ai pass; prettier --check and eslint pass
on the touched frontend file; live GET /v1/models on the gateway verified to return the
standard {"data": [...]} shape used by DiscoverModels. Not yet run against a live
1Panel/OpenClaw deployment.

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.