feat: improve mobile native impl (#14481)

fix #13529 

#### PR Dependency Tree


* **PR #14481** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Mobile blob caching with file-backed storage for faster loads and
reduced network usage
* Blob decoding with lazy refresh on token-read failures for improved
reliability
  * Full-text search/indexing exposed to mobile apps
* Document sync APIs and peer clock management for robust cross-device
sync

* **Tests**
* Added unit tests covering payload decoding, cache safety, and
concurrency

* **Dependencies**
* Added an LRU cache dependency and a new mobile-shared package for
shared mobile logic
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/mobile-native/Cargo.toml

@@ -23,6 +23,7 @@ base64-simd    = { workspace = true }
 chrono         = { workspace = true }
 sqlx           = { workspace = true }
 thiserror      = { workspace = true }
+tokio          = { workspace = true, features = ["rt-multi-thread"] }
 uniffi         = { workspace = true, features = ["cli", "tokio"] }
 
 [target.'cfg(any(target_os = "ios", target_os = "macos"))'.dependencies]
@@ -38,5 +39,12 @@ objc2-foundation = { workspace = true, features = [
 [target.'cfg(not(any(target_os = "ios", target_os = "macos")))'.dependencies]
 homedir = { workspace = true }
 
+[target.'cfg(any(target_os = "android", target_os = "ios"))'.dependencies]
+lru = { workspace = true }
+
 [build-dependencies]
 uniffi = { workspace = true, features = ["build"] }
+
+[dev-dependencies]
+lru   = { workspace = true }
+tokio = { workspace = true, features = ["full"] }