Play Framework

chore: enable Gradle configuration cache + broaden Gradle gitignore (PF-90)

Gradle 9.5 supports configuration cache as a stable feature and it
becomes the only mode in Gradle 10. The play-gradle-plugin is
already configuration-cache safe (per Phase 1-6 design: @Inject
services, Property<T> inputs, no Task.project at execution time).
Enable permanently in /opt/play1 so subsequent task invocations
skip the configuration phase entirely (~3x speedup on simple tasks).

Also broaden the Gradle gitignore from
\"framework/gradle-plugin/build/\" to plain \"build/\" so the
root-level Gradle build/ output (e.g., from playClasspath, etc.)
isn't accidentally committed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>