audit(#622): sweep hardcoded colors + add checkColorLiterals guard (#626)

Removed docs/color-hardcoded-audit.md per request. Replaced 2 hardcoded
Color literals with theme tokens; added CI guard blocking new literals.

Co-authored-by: Hy4ri <hy4ri@users.noreply.github.com>

.github/workflows/android.yml

@@ -65,6 +65,9 @@ jobs:
       - name: Run ktlintCheck
         run: ./gradlew ktlintCheck
 
+      - name: Run checkColorLiterals (hardcoded Color guard, issue #622)
+        run: ./gradlew checkColorLiterals
+
       - name: Upload ktlint reports
         if: always()
         uses: actions/upload-artifact@v7