tools: add make analyze/test/doctor and unify gradle wrappers

- Add scripts/analyze_all.sh and scripts/test_all.sh that run flutter
  analyze/test across every app and report a summary
- Add scripts/repo_doctor.sh that flags config drift (sdk constraint,
  analysis_options, pubspec name, applicationId, gradle version, docs,
  tracked generated files) and exits non-zero for use as a pre-commit gate
- Wire these into the Makefile as 'make analyze/test/doctor' and document
  them in MAINTENANCE.md
- Bring bmi_calculator and push_notifications gradle wrappers up to the
  repo-standard 9.7.0; note push_notifications as a Firebase app requiring
  google-services.json

bmi_calculator/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.7.0-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.3.1-all.zip