1.1.6: still image export — PNG / JPG snapshot of the current frame

Adds a "Still image" subgroup under the project column in the export
dialog. Both options render the current playhead frame via the same
drawSceneFrame path used by GIF/APNG, so the still is pixel-identical
to the matching animated frame. JPG fills transparent scenes white;
PNG keeps alpha. Honours the per-export target size for higher-res
poster frames.

src/version.ts

@@ -1,2 +1,2 @@
-export const APP_VERSION = '1.1.5'
+export const APP_VERSION = '1.1.6'
 export const APP_NAME = 'RUWIO'