Update frontend dependencies, enhance Vite configuration, and refactor components

- Added new dependencies including @base-ui/react, @fontsource-variable/geist, and tailwindcss for improved UI and styling.
- Updated Vite configuration to include path aliasing for easier imports.
- Refactored App.jsx to implement a theme context and improved routing structure.
- Enhanced various components (e.g., ConfirmDialog, DataTable) to utilize new UI components and improve user experience.
- Cleaned up CSS imports and ensured proper styling integration.

Made-with: Cursor

frontend/docs/SHADCN_MIGRATION_BASELINE.md

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+# Tabler to shadcn/ui baseline
+
+## Purpose
+This file freezes the legacy UI baseline before migration to native-first shadcn/ui.
+All new UI work should follow these constraints.
+
+## Confirmed legacy entry points
+- `frontend/src/main.jsx` imports Tabler CSS and Tabler JS runtime.
+- `frontend/src/App.jsx` and `frontend/src/App.css` contain the primary legacy shell and Tabler-oriented layout classes.
+
+## Legacy patterns to block in new code
+- `window.Tabler.*`
+- `data-bs-*` attributes for interactive behavior
+- Bootstrap/Tabler JS-driven collapse, dropdown, modal, offcanvas behavior
+- New custom wrappers for components that already exist in shadcn/ui primitives
+
+## Migration-first rules
+- Use shadcn/ui primitives directly for new UI: `Button`, `Input`, `Dialog`, `AlertDialog`, `DropdownMenu`, `Table`, `Tooltip`, `Sheet`, `Select`, `Checkbox`, `Sonner`.
+- Use shadcn sidebar primitives for application shell work:
+  - `SidebarProvider`
+  - `Sidebar`
+  - `SidebarInset`
+  - `SidebarTrigger`
+- Keep custom abstractions thin and only where there is repeated business logic.
+- Do not introduce new Tabler classes in migrated files.
+
+## Current impact snapshot
+Tabler-related usage appears across most frontend screens and shared components. The migration must proceed by shared primitives first, then screen waves.