feat(mcp): add HTTP transport UI fields to MCP server config

[Shooksie]

Summary

• Adds McpTransport type and McpServerConfig interface (src/types/mcp.ts)
• Adds McpServerForm component with transport type selector (stdio / HTTP), URL field, optional bearer token field, and live validation
• Adds McpServerList component for managing the server list (add / edit / remove)
• Integrates McpServerList into App.tsx below the existing panel grid

Why

Issue #96 shipped HTTP/remote MCP transport support in ao-cli, but ao-desktop had no UI to configure it. This follow-on surfaces the transport selector so users can connect to remote MCP servers (HTTP/SSE) in addition to local stdio processes.

Transport fields

Transport	Fields
stdio	Command (executable + args)
http	URL (validated as valid URL), Bearer Token (optional)

Test plan

• pnpm build (tsc + vite) passes — 0 type errors, 0 build errors
• Manual: open app, click "Add server", toggle between stdio / HTTP, verify correct fields appear
• Manual: submit with empty required fields — verify per-field error messages
• Manual: submit valid stdio config — verify entry appears in list with "stdio" badge
• Manual: submit valid HTTP config — verify entry appears in list with "HTTP" badge and URL shown
• Manual: click Edit — verify form pre-populates; save updates the entry
• Manual: click Remove — verify entry removed from list

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