fix: restore original CSS and combine with mobile styles

- Restored original desktop CSS that was accidentally overwritten
- Added back all mobile-specific styles
- CSS file now 3945 lines (original + mobile styles)
- Build passes successfully

openspec/changes/archive/2026-05-25-mobile-pages-overhaul/specs/mobile-navigation/spec.md

@@ -0,0 +1,16 @@
+## ADDED Requirements
+
+### Requirement: Bottom navigation grouping
+The mobile bottom navigation SHALL support grouping related pages under a single navigation item that opens a sub-menu.
+
+#### Scenario: Tools group navigation
+- **WHEN** user views the mobile bottom navigation
+- **THEN** a "Tools" item is visible that groups Tool Workshop and Config Profiles
+
+#### Scenario: Opening grouped menu
+- **WHEN** user taps a grouped navigation item
+- **THEN** a bottom sheet or menu opens showing the grouped pages
+
+#### Scenario: Active state for grouped items
+- **WHEN** user is on a page within a group
+- **THEN** the group's navigation item shows as active