Add shared transition search demo

[RedSTARO]

Motivation

• Add a reusable cross-screen shared element (shared bounds) demo to validate SearchBox → Search page transitions using Compose's official shared transition APIs.
• Prepare the app to adopt SharedTransitionLayout as the global host for element-level transitions across Nav destinations.

Description

• Wrap the main NavHost in SharedTransitionLayout and expose the SharedTransitionScope/AnimatedVisibilityScope to composables for shared-bounds use.
• Implement a reusable SharedKeys object and convert the home SearchBox into a shared-bounds card that navigates to the demo search route using rememberSharedContentState and sharedBounds.
• Add SearchDemoPage that consumes the same shared key and displays a TextField to demonstrate the cross-screen shared bounds interpolation.
• Add the Compose animation library to the version catalog (gradle/libs.versions.toml) and the app module (app/build.gradle.kts) to enable the shared transition APIs.

Testing

• No automated tests were run for this change.
• Changes were validated by local code edits and compilation dependency updates (no build executed in CI as part of this PR).

---

Codex Task