feat(mcp): add multi-step wizard for adding MCP servers (#241)

Add a wizard flow for adding MCP servers with the following steps:
1. Choose source: Custom configuration or MCP Registry
2. For custom servers, choose transport type: Stdio or HTTP
3. Enter server details based on the selected transport

Features:
- Step 1: Choose between custom server or registry
- Step 2: Choose transport type (stdio for local, HTTP for remote)
- Step 3a: Stdio server form (name, command, args)
- Step 3b: HTTP server form (name, URL)
- Step 3c: Registry selection with search/filter

Also adds AddMcpServerHttp modal action for HTTP servers.

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt