[Feature]: support android cross build

[feihongxu0824]

Problem / Motivation

Currently, Zvec does not provide official support or documented guidance for cross-compiling to Android targets (e.g., aarch64-linux-android, armv7-linux-androideabi). This limits its adoption in mobile and embedded AI scenarios—such as on-device RAG, semantic search in mobile apps, or integration with Android-based edge AI frameworks—where low-latency, privacy-preserving vector operations are critical.
Many developers building AI-powered Android applications rely on native libraries via the Android NDK. Without proper cross-compilation support, users must manually configure complex build environments, which creates a high barrier to entry and increases integration risk.

Proposed Solution

Alternatives Considered

No response

Affected Area

No response

[abuvanth]

For mobile RAG https://github.com/cyberlife-coder/VelesDB/tree/main/crates/velesdb-mobile by using FFI