feat(frontend): implement dynamic multi-target client connection guide

[spelech]

Summary

• Replaces static connection snippets with an interactive, dynamic Client Connection Guide in the MCP Router UI.
• Supports 3 standard client formats:
  1. Standard mcpServers JSON (Claude Desktop, Antigravity / AGY, Cursor, Cline, Roo Code).
  2. VS Code mcp.json.
  3. Generic SSE & HTTP endpoints.
• Adds dynamic controls for Domain / Host (Current Host, Local LAN, Custom), Server Scope (all unified gateway vs individual server route), Meta-Mode toggle (?meta=true vs ?meta=false), and App Key credential selector.
• Embeds the guide across Overview, My App Keys, and My MCP Servers pages.
• Includes comprehensive unit & integration tests and production assets build.