# Phase 3: Mobile Web Optimization & Local Persistence

## Responsive UI Stacking
The interface has been upgraded to a **Mobile-First Responsive Layout**. Using CSS Media Queries, the "Scanner" and "Vault" views now transition from a dual-column desktop view to a single-column stacked view on devices with widths less than 768px.
- **Touch Targets**: The "Upload Zone" has been optimized with increased padding and a larger click area to accommodate mobile touch gestures.
- **Dynamic Scaling**: The detection overlay logic utilizes a relative scaling factor ($Scale = \frac{ContainerWidth}{ImageWidth}$) which recalculates on every scan to ensure bounding boxes perfectly align with the responsive canvas on any screen size.

## Local Persistence (The Vault)
The system now features a robust **Local Persistence Layer** via the `LocalHistoryService`. This replaces the previous FastAPI backend dependency for history tracking.
- **LocalStorage Integration**: All scan results, including MPOB summary counts, latency metrics, and detection box coordinates, are serialized and stored in the browser's `localStorage`.
- **Asset Archiving**: To support offline review, the system captures a Base64 string of the processed image, allowing users to review detection boxes in the "Vault" even after the original file is no longer available.
- **Overflow Protection**: The local vault is capped at the 20 most recent records to prevent browser memory overflow while maintaining a functional audit trail for field harvesters.

## Mobile Integration Checklist
| Task | Status | Implementation Detail |
| :--- | :--- | :--- |
| **Viewport Scaling** | Configured | Meta tag set to `width=device-width`. |
| **Column Stacking** | Active | Media queries applied to `Analyzer` and `History` rows. |
| **Canvas Auto-Resize** | Active | Logic tied to `parentElement.clientWidth`. |
| **Persistent Vault** | Active | Powered by `LocalHistoryService` and `localStorage`. |
