FIX - stabilize homescreen dragging across scaling (#18)

* FIX - stabilize homescreen dragging across scaling

Render the home drag preview in an unzoomed viewport portal and normalize FiveM CEF DOM geometry before hit testing and drop settling. Cover Chrome 103, fractional scaling, 4K, ultrawide, and non-16:9 viewport behavior.

* FIX - Implement LB guest app layout and lifecycle bridge

Ensure custom LB apps are properly sized and visible by applying the required CSS contract on initialization and upon receiving the 'componentsLoaded' signal.

* FIX - match uppercase script tags in LB bridge test

frontend/src/utils/springboardDrag.test.ts

@@ -140,4 +140,56 @@ describe('springboard widget drag', () => {
     expect(delta.x).toBeCloseTo(100)
     expect(delta.y).toBeCloseTo(200)
   })
+
+  it.each([
+    ['80% preview', 0.6624],
+    ['80% production clamp', 2 / 3],
+    ['100%', 0.828],
+    ['120%', 0.9936],
+  ])('keeps the rendered drag delta 1:1 at %s zoom', (_label, zoom) => {
+    const layoutWidth = 350
+    const layoutHeight = 808
+    const viewportLeft = 128.25
+    const viewportTop = 64.5
+    const viewportWidth = layoutWidth * zoom
+    const viewportHeight = layoutHeight * zoom
+    const pointerStart = {
+      x: viewportLeft + 48.5 * zoom,
+      y: viewportTop + 132.25 * zoom,
+    }
+    const viewportDelta = { x: 73.25, y: -41.75 }
+    const start = springboardViewportToLocal(
+      pointerStart.x,
+      pointerStart.y,
+      viewportLeft,
+      viewportTop,
+      viewportWidth,
+      viewportHeight,
+      layoutWidth,
+      layoutHeight,
+    )
+    const end = springboardViewportToLocal(
+      pointerStart.x + viewportDelta.x,
+      pointerStart.y + viewportDelta.y,
+      viewportLeft,
+      viewportTop,
+      viewportWidth,
+      viewportHeight,
+      layoutWidth,
+      layoutHeight,
+    )
+    const localDelta = springboardViewportDeltaToLocal(
+      viewportDelta.x,
+      viewportDelta.y,
+      viewportWidth,
+      viewportHeight,
+      layoutWidth,
+      layoutHeight,
+    )
+
+    expect((end.x - start.x) * zoom).toBeCloseTo(viewportDelta.x, 6)
+    expect((end.y - start.y) * zoom).toBeCloseTo(viewportDelta.y, 6)
+    expect(localDelta.x * zoom).toBeCloseTo(viewportDelta.x, 6)
+    expect(localDelta.y * zoom).toBeCloseTo(viewportDelta.y, 6)
+  })
 })