feat(client): implement react frontend application

- Created main entry point `src/client/main.tsx`.
- Created main `App` component `src/client/App.tsx`.
- Implemented state management (`initial`, `waiting`, `success`, `failed`) using `useState`.
- Implemented `handleStart` to call backend `/api/digiid/start` and transition to `waiting` state.
- Implemented `useEffect` hook for polling backend `/api/digiid/status/:sessionId` in `waiting` state.
    - Updates UI state based on polling response (`success`/`failed`).
    - Handles polling errors and cleanup.
- Implemented `handleReset` to return to `initial` state.
- Implemented views for each state:
    - `initial`: Welcome message, Start button.
    - `waiting`: QR code display, status message, Cancel button.
    - `success`: Success message, verified address, address type, Start Over button.
    - `failed`: Failure message, error details, Try Again button.
- Added client-side address type helper `getDigiByteAddressType` in `src/client/utils.ts`.
- Added basic CSS styling in `src/client/index.css` with light/dark mode support.
- Added frontend-related scripts (`dev:frontend`, `dev`, `build`, `lint`, `preview`) to `package.json`.
- Fixed linter type issue with `setInterval` return value.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/client/utils.ts b/src/client/utils.ts
new file mode 100644
index 0000000..cd9c8ba
--- /dev/null
+++ b/src/client/utils.ts
@@ -0,0 +1,20 @@
+// Simple utility to determine DigiByte address type based on prefix
+
+export type DigiByteAddressType = 'DigiByte (DGB)' | 'DigiAsset (DGA)' | 'Unknown';
+
+export function getDigiByteAddressType(address: string | undefined | null): DigiByteAddressType {
+  if (!address) {
+    return 'Unknown';
+  }
+  if (address.startsWith('dgb1')) {
+    return 'DigiByte (DGB)';
+  }
+  // Add other prefixes if DigiAssets use a distinct one, e.g., 'dga1'
+  // For now, assume non-DGB is DigiAsset, but this might need refinement
+  // depending on actual DigiAsset address formats.
+  else {
+    // Assuming DigiAssets might start differently or be the fallback
+    // This is a placeholder assumption.
+    return 'DigiAsset (DGA)'; // Placeholder - ADJUST BASED ON ACTUAL DGA PREFIX
+  }
+} 
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