Stop the CI from re-fetching crests, cache their URLs instead

Fetching 56 images on every run earned nothing but rate limits, and the
CI artefact is a test build that does not need the badges — the shield
fallback covers it. The resolved image URLs are cached in
tools/crest-sources.json, which is plain text and safe to commit, so a
local run needs one request per club instead of two and can resume after
a rate limit. The artwork itself stays out of the repository.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -43,9 +43,6 @@ jobs:
             "platforms;android-35" "build-tools;35.0.0" "platform-tools" > /dev/null
           echo "sdk.dir=$ANDROID_SDK_ROOT" > local.properties
 
-      - name: Fetch club crests
-        run: python3 tools/fetch-crests.py || true
-
       - name: Unit tests
         run: ./gradlew testDebugUnitTest --no-daemon --stacktrace