Fix flipped drawing when copying/saving annotated images

The strokes were stored in top-left image coordinates but drawn into an
AppKit CGContext with a bottom-left origin, so exports came out mirrored
and offset. Flip Y in the context before stroking so annotations land
where they were drawn.

💘 Generated with Crush

Assisted-by: Crush:deepseek-v4-flash-0731

build-app.sh

@@ -108,9 +108,9 @@ cat > "$APP/Contents/Info.plist" <<'PLIST'
     <key>CFBundleIconFile</key>
     <string>Icon</string>
     <key>CFBundleShortVersionString</key>
-    <string>1.4.2</string>
+    <string>1.4.3</string>
     <key>CFBundleVersion</key>
-    <string>42</string>
+    <string>43</string>
     <key>LSUIElement</key>
     <true/>
     <key>NSHighResolutionCapable</key>