feat(mcp): add remote auth, interaction flows, and prompt/resource support

[wgqqqqq]

Summary

This PR expands BitFun's MCP integration across the core service layer, desktop bridge, and web UI.

It adds a complete remote-auth and reauth flow, surfaces MCP interaction requests in the app UI, and exposes MCP prompt/resource capabilities both to the agent runtime and to end users in the chat input and settings UI.

What changed

• Add remote MCP OAuth and reauth support across config parsing, server lifecycle/auth management, and desktop APIs.
• Preserve remote metadata and transport semantics so stdio, SSE, and streamable HTTP servers keep the right behavior and UI affordances.
• Split MCP server management into focused auth, lifecycle, reconnect, interaction, catalog, and tools modules to make the service easier to evolve.
• Add MCP interaction dialog plumbing in the app shell so server-driven user interaction requests can be surfaced and completed in the desktop UI.
• Add MCP resource and prompt APIs on the desktop/web boundary.
• Add built-in agent tools for listing/reading MCP resources and listing/getting MCP prompts.
• Expose MCP prompts in the chat slash-command picker and execute them in a Claude-style flow: the visible user message stays as the slash command, while the actual model input is expanded from prompts/get.
• Replace the MCP resource browser mock data with real resource listing and reading.
• Improve MCP settings/tool presentation, metadata handling, and config item UI.

Verification

• cargo check -p bitfun-core --lib
• cargo check -p bitfun-desktop --lib
• pnpm run type-check:web