fix(ci): generate changelog before analyze (assets/ must exist)

The assets/ directory is created by generate-changelog. Splitting CI into
separate steps meant analyze ran before any step created it, causing a
pubspec.yaml asset_directory_does_not_exist warning that fails the check.

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

.forgejo/workflows/ci.yml

@@ -19,6 +19,9 @@ jobs:
           mkdir -p ~/.config/nix
           echo "experimental-features = nix-command flakes" >> ~/.config/nix/nix.conf
 
+      - name: Generate changelog
+        run: nix develop --command task generate-changelog
+
       - name: Analyze
         run: nix develop --command task analyze