[Frigate] Add adjustable split between video and timeline in mobile History view

## Describe what you are trying to accomplish and why in non technical terms** On mobile devices, the History / Recording viewer can be difficult to use, especially with wide or ultra-wide camera aspect ratios. The fixed layout means: - some cameras appear too small when the timeline is visible - there can be wasted space / black bars depending on aspect ratio - users may want more room for the video at some moments and more room for the timeline at others - using zoom alone is not enough because the real need is to rebalance space between the player and the timeline ## Describe the solution you'd like Add an adjustable split between the video area and the timeline in mobile History view. Expected behavior: - In mobile portrait layout, allow the divider between the video player and timeline to be dragged up or down - Dragging the divider up gives more space to the timeline - Dragging the divider down gives more space to the video - The video should remain fit within its available bo