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 -->

Cargo.lock

@@ -111,10 +111,12 @@ dependencies = [
  "base64-simd",
  "chrono",
  "homedir",
+ "lru",
  "objc2",
  "objc2-foundation",
  "sqlx",
  "thiserror 2.0.17",
+ "tokio",
  "uniffi",
 ]
 
@@ -2572,6 +2574,15 @@ dependencies = [
  "weezl",
 ]
 
+[[package]]
+name = "lru"
+version = "0.16.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1dc47f592c06f33f8e3aea9591776ec7c9f9e4124778ff8a3c3b87159f7e593"
+dependencies = [
+ "hashbrown 0.16.1",
+]
+
 [[package]]
 name = "mac"
 version = "0.1.1"