ui: Move Settings and MCP Servers routes to dialog-based views (#27744)

* ui : open MCP servers in a dialog from the chat form

Replace the MCP servers submenu with a single "MCP Servers" item that opens
a new DialogMcpServers dialog instead of navigating to the /mcp-servers route.

Assisted-by: pi

* ui : browse MCP resources from the server card

Make the Resources capability badge clickable so it opens the MCP resources
browser dialog, and drop the page-only chrome from SettingsMcpServers.

Assisted-by: pi

* ui : remove mcp-servers route and sidebar entry

MCP servers are now managed in a dialog, so drop the dedicated route and the
sidebar icon that navigated to it.

Assisted-by: pi

* ui : remove unused MCP servers submenu component

The submenu was replaced by the MCP servers dialog, so delete the component
and its export.

Assisted-by: pi

* feat(ui): add DialogSettingsChat dialog

* refactor(ui): switch SettingsChat to in-app section navigation

* feat(ui): open settings as dialog from sidebar

* refactor(ui): remove settings route and URL-based settings navigation

* fix(ui): adjust MCP dialogs for new base sizing

* chore: Formatting & linting