feat: implement DeesDashboardgrid component with drag-and-drop functionality

- Added DeesDashboardgrid class for managing a grid of dashboard widgets.
- Implemented widget dragging and resizing capabilities.
- Introduced layout management with collision detection and margin resolution.
- Created styles for grid layout, widget appearance, and animations.
- Added support for customizable margins, cell height, and grid lines.
- Included methods for adding, removing, and updating widgets dynamically.
- Implemented context menu for widget actions and keyboard navigation support.
- Established a responsive design with breakpoint handling for different layouts.

ts_web/elements/dees-dashboardgrid/README.md

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+# dees-dashboardgrid
+
+`<dees-dashboardgrid>` renders a configurable dashboard layout with draggable and resizable tiles. The component is now grouped in its own folder alongside supporting utilities and styles.
+
+## Key Features
+
+- Pointer-driven drag and resize interactions with keyboard fallbacks (arrow keys to move, `Shift` + arrows to resize).
+- Collision-aware placement that swaps compatible tiles or displaces blocking tiles into the next free slot.
+- Context menu (right-click on a tile header) that exposes destructive actions such as tile removal via `dees-contextmenu`.
+- Layout persistence helpers via `getLayout()`, `setLayout(...)`, and the `layout-change` event.
+- Responsive presets through the `layouts` map and `applyBreakpointLayout(...)` helper to hydrate per-breakpoint arrangements.
+
+## Public API Highlights
+
+| Property | Description |
+| --- | --- |
+| `widgets` | Array of tile descriptors (`DashboardWidget`). |
+| `columns` | Number of grid columns. |
+| `layouts` | Optional record of named layout definitions. |
+| `activeBreakpoint` | Name of the currently applied breakpoint layout. |
+| `editable` | Toggles drag/resize affordances. |
+
+| Method | Description |
+| --- | --- |
+| `addWidget(widget, autoPosition?)` | Adds a tile, optionally auto-placing it into the next free slot. |
+| `removeWidget(id)` | Removes a tile and emits `widget-remove`. |
+| `applyBreakpointLayout(name)` | Applies a layout from the `layouts` map. |
+| `getLayout()` / `setLayout(layout)` | Retrieve or apply persisted layouts. |
+| `compact(direction?)` | Densifies the grid vertically (default) or horizontally. |
+
+| Event | Detail payload |
+| --- | --- |
+| `widget-move` | `{ widget, displaced, swappedWith }` |
+| `widget-resize` | `{ widget, displaced, swappedWith }` |
+| `widget-remove` | `{ widget }` |
+| `layout-change` | `{ layout }` |
+
+## Usage Notes
+
+- **Right-click** a tile header to open the contextual menu and delete the tile.
+- When resizing, blocking tiles will automatically reflow into free space once the interaction completes.
+- Listen to `layout-change` to persist layouts to storage; rehydrate using `setLayout` or the `layouts` map.
+- For responsive dashboards, populate `grid.layouts = { base: [...], mobile: [...] }` and call `applyBreakpointLayout` based on your own breakpoint logic (see the co-located demo for an example).
+
+## Demo
+
+The updated `dees-dashboardgrid.demo.ts` showcases live breakpoint switching, layout persistence, and the context menu. Run the demo gallery to explore the interactions end-to-end.