Add draw toolbar with thickness, undo/redo, and color picker

When drawing is enabled a dedicated top bar shows a thickness slider,
color picker, and undo/redo buttons (⌘Z / ⌘⇧Z). Strokes render and export
with the chosen width and color.

💘 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>1.3.3</string>
+    <string>1.4.0</string>
     <key>CFBundleVersion</key>
-    <string>33</string>
+    <string>40</string>
     <key>LSUIElement</key>
     <true/>
     <key>NSHighResolutionCapable</key>