Fix Linux CI: add missing system deps for pygobject/cairo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Paullux

.github/workflows/build.yml

@@ -41,7 +41,13 @@ jobs:
       - name: Install system dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y libdbus-1-dev libglib2.0-dev pkg-config
+          sudo apt-get install -y \
+            libdbus-1-dev \
+            libglib2.0-dev \
+            libcairo2-dev \
+            libgirepository1.0-dev \
+            gir1.2-appindicator3-0.1 \
+            pkg-config
 
       - name: Install dependencies
         run: pip install -r requirements-linux.txt