Add reusable Input, Modal, Toast, and FileUpload frontend components

[Ibinola]

Motivation

• Provide reusable UI building blocks for forms and notifications in the frontend by implementing Input, Modal, Toast, and FileUpload components.
• Consolidate common patterns (validation, accessibility, toast provider) so feature pages can reuse them.

Description

• Add Input component with label/helper/error states, optional icons, and password show/hide (frontend/cmmty/components/Input).
• Add Modal component with ESC and overlay-close behavior, sizes (sm|md|lg) and accessible attributes (frontend/cmmty/components/Modal).
• Add toast system (ToastProvider, useToast, ToastStack) with types, auto-dismiss and manual dismiss (frontend/cmmty/components/Toast).
• Add FileUpload drag-drop/click uploader with MIME and size validation and a reusable validateFile util (frontend/cmmty/components/FileUpload).
• Add unit tests for Input, Modal, Toast, and FileUpload validation, and small type fixes; committed and prepared as a single PR that closes the related issues.
• Closes [FE-17] Create reusable Input component with validation states CodeGirlsInc/SMALDA#383
• Closes [FE-18] Create reusable Modal/Dialog component CodeGirlsInc/SMALDA#384
• Closes [FE-19] Create Toast/Snackbar notification component CodeGirlsInc/SMALDA#385
• Closes [FE-20] Create drag-and-drop File Upload component CodeGirlsInc/SMALDA#386

Testing

• Added unit tests under each component folder for Input, Modal, Toast, and FileUpload validation (files present in frontend/cmmty/components/*/*.test.tsx); tests were executed with npm test but the run failed due to Jest/Babel transform configuration not present in this repo (JSX/TSX parsing errors).
• Type check with npx tsc --noEmit failed due to missing test runner typings (recommend adding @types/jest).
• Attempted dependency provisioning (npm install --package-lock-only) failed to fetch @radix-ui/react-dialog due to registry 403, so some runtime deps were not installed.