v0.3.0

feat(mcp): manage MCP servers for launched agents

- New MCP tab (McpPanel.vue): add/edit/remove MCP servers with per-server
  env vars and per-agent targets, form validated with zod
- Backend: list_mcp_servers / save_mcp_server / delete_mcp_server commands;
  Bridge keeps its own registry (mcp.json in app config dir, .bak backup)
  and writes/reads entries surgically by id in each agent's native config:
  Claude Code (~/.claude.json mcpServers), OpenCode (mcp, local-server
  shape), Claude Desktop (normal config mcpServers)
- Existing foreign entries in agent configs are preserved; deletion removes
  only Bridge-written entries and keeps the registry consistent on failure
- Header: installed-surface badge now expands a tooltip listing installed
  desktop apps and CLIs; launcher page reorganized into Applicativi/MCP tabs
- Bump version to 0.3.0