fix: update CACHEBUST to v3 to force fresh Docker build

Update CACHEBUST arg to 2025-12-08-v3 to ensure Docker doesn't use cached layers and rebuilds with the latest code fixes. This ensures the duplicate height line fix is included in the build.

Dockerfile

@@ -19,7 +19,7 @@ RUN flutter config --enable-web
 # Copy dependency files first for better caching
 # Note: pubspec.lock will be generated by flutter pub get if missing
 # Cache buster - INCREMENT THIS VALUE TO FORCE REBUILD ON DEPLOY
-ARG CACHEBUST=2024-12-08-v2
+ARG CACHEBUST=2025-12-08-v3
 COPY pubspec.yaml ./
 
 # Get dependencies (generates pubspec.lock automatically)