Feat/homepage navbar redesign

[Creylay]

Summary

Complete UI redesign of the homepage and navbar. Replaces the old theme palette with an Amber Dark + Neutral Light
design system, switches fonts to IBM Plex Sans/Mono, redesigns the homepage layout into a sidebar + 2×2 module card
grid, and reworks the navbar with tab-style navigation and an amber active indicator. Also includes responsiveness
improvements, tour integration fixes, multilingual metric descriptions, delete confirmation dialogs, and general
cleanup of deprecated/unused code.

---

Type of Change

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

---

Changes (by file)

Theme & Fonts

• front/src/styles/theme.js: replaced full palette (Amber Dark + Neutral Light), added IBM Plex typography
  variants, custom data-type and accent colors, removed unused MuiDataGrid overrides and language parameter
• front/public/index.html: added IBM Plex Sans & Mono via Google Fonts CDN
• front/src/index.css: updated base font-family references
• front/src/contexts/ThemeContext.jsx: removed language arg from getTheme call
• front/src/utils/plotlyTheme.js: aligned Plotly chart colors with new theme

Navbar

• front/src/components/ResponsiveAppBar.jsx: redesigned with IBM Plex tab labels, Workbench badge, amber active
  indicator, improved responsive behavior
• front/src/components/hardware/HardwareMonitorButton.jsx: restyled to match navbar icon button pattern
• front/src/components/tour/NavbarTourButton.jsx: new component — moved tour widget into the navbar
• front/src/components/tour/TourProvider.jsx: integrated NOOP_REGISTRY fallback for safer context handling
• front/src/contexts/TourRegistryContext.jsx: new context for tour step registry

Homepage

• front/src/pages/home/Home.jsx: redesigned layout — sidebar + 2×2 amber module card grid with icons and
  descriptions
• front/src/components/HomeButton.jsx: replaced with amber-design module card component
• front/src/components/threeSectionLayout/OptionBox.jsx: refactored to use ButtonBase, enhanced styling and layout

Three-Section Layout

• front/src/components/threeSectionLayout/CollapsibleList.jsx: updated typography to use theme variants
• front/src/components/threeSectionLayout/GroupedCollapsibleList.jsx: improved navbar icon color, title typography,
  stable scrollbar gutter
• front/src/components/threeSectionLayout/DeleteConfirmationModal.jsx: added delete confirmation dialogs with i18n
  support
• front/src/components/threeSectionLayout/ItemBox.jsx: minor styling tweaks
• front/src/components/threeSectionLayout/ItemMenu.jsx: minor styling tweaks

Models & Datasets

• front/src/pages/models/ModelsContent.jsx: layout adjustments
• front/src/components/models/ModelsRightBar.jsx: improved title/toggle alignment
• front/src/components/models/ModelsLeftBar.jsx: added left bar icons
• front/src/pages/datasets/DatasetsContent.jsx: layout adjustments
• front/src/components/notebooks/RightBar.jsx: improved title/toggle alignment
• front/src/components/notebooks/DatasetNotebookLeftBar.jsx: added left bar icons

Generative

• front/src/pages/generative/GenerativeContent.jsx: layout adjustments
• front/src/components/generative/SelectModelMenu.jsx: improved tour element handling and scrolling
• front/src/components/generative/SessionForm.jsx: improved tour handling
• front/src/components/generative/SessionBar.jsx: updated Footer import path
• front/src/components/generative/Footer.jsx: removed (unused)

Backend (metrics)

• back/metrics/classification/*.py: added multilingual descriptions (en/es) for all classification metrics
• back/metrics/regression/*.py: added multilingual descriptions (en/es) for all regression metrics
• back/metrics/translation/*.py: added multilingual descriptions (en/es) for all translation metrics

i18n

• front/src/utils/i18n/locales/{en,es}/home.json: updated with new sidebar links, module tags and chip labels
• front/src/utils/i18n/locales/{en,es}/datasets.json: added delete confirmation strings
• front/src/utils/i18n/locales/{en,es}/models.json: added delete confirmation strings
• front/src/utils/i18n/locales/{en,es}/generative.json: added missing keys

Tests

• front/src/test-utils/renderWithProviders.jsx: new test utility with theme and i18n providers
• front/src/components/HomeButton.test.jsx: new tests for HomeButton
• front/src/components/ResponsiveAppBar.test.jsx: new tests for navbar
• front/src/components/hardware/HardwareMonitorButton.test.jsx: new tests
• front/src/components/jobs/JobQueueWidget.test.jsx: new tests
• front/src/components/tour/TourButton.test.jsx: new tests
• front/src/pages/home/Home.test.jsx: new tests for home page

Cleanup

• front/src/App.jsx: removed unused routes for experiments and explainers
• front/src/constants/tours/homeTour.js: removed explainability/pipelines tour steps
• front/src/components/tour/tourStyles.js: updated primary colors to match new theme

---

Testing (optional)

• Verify dark and light mode render correctly with the new Amber/Neutral palette
• Check navbar responsiveness on small screens (hamburger menu)
• Verify homepage module cards link to correct routes
• Confirm JobQueueWidget is visible and not hidden behind the AppBar

---

Notes (optional)

• The @mui/x-data-grid dependency was removed in a prior commit; this PR cleans up the remaining datagridLocale
  references and MuiDataGrid theme overrides that survived a merge conflict.
• The language parameter was removed from getTheme() since its only consumer (DataGrid locale) no longer exists.