Add optional feature tours and a version changelog

[Steadyx]

What changed

Adds Settings → What’s new with a searchable, offline changelog derived from Git release history, translated into all seven supported languages. Users can replay a short feature tour using the existing tutorial highlights, skip it, or open the changelog from any tour step.

Published updates offer a one-time invitation when users return to the library, deferring during the starting tutorial, reading, imports, exports, and Play update prompts. Fresh installs keep the starting tutorial. Acknowledged versions persist across settings resets and do not move backwards on downgrades.

The history covers 1.0.8–1.3.0 and the subsequent Upcoming changes. Release preparation must assign the Upcoming entry its actual version name/code before automatic invitations activate; this PR does not bump or publish a release. The release guide documents curation and validation.

Risk

Changes affect tutorial navigation and release acknowledgement persistence. Tour cards now scroll and wrap controls for larger text. JVM tests cover version eligibility, fresh installs, skipped versions, downgrades, and unpublished notes; a full installed-app upgrade/rotation/locale matrix remains to be checked before release. Notes and translations are maintained in the repository.

Validation

• ./gradlew qualityCheck — 919 JVM tests passing
• ./gradlew qualityGate — formatting, Detekt, compilation, Android Lint, tests, and debug APK assembly
• Android Lint completed successfully
• Focused regression tests added
• git diff --check
• :app:compileDebugAndroidTestKotlin and :app:assembleDebugAndroidTest
• WhatsNewDeviceTest on CPH2493 — OK (3 tests): invitation actions, changelog history/replay, and tour controls at 2× font size. Installed over the separate debug app without clearing its data.

Quality policy

• No baseline, ignoreFailures, broad exclusion, or unrelated threshold relaxation added
• The version-catalog magic-number suppression is declaration-scoped and explained
• No generated files, debug logging, commented-out code, or unrelated formatting churn included