(draft) fix(android): enforce 16kb page alignment

[reez]

https://github.com/bitcoindevkit/bdk-ffi/pull/904/files adds Android 16KB alignment via .cargo/config.toml, but Cargo only reads config from the workspace root, not dependencies. bdk‑dart builds a native/ wrapper with bdk‑ffi as a dependency, so those flags never applied. This PR adds native/.cargo/config.toml to pass the same linker flags.

• Built the Android release from native/ using the NDK toolchain.
• Inspected the resulting libbdk_dart_ffi.so with llvm-readelf and confirmed all LOAD segments show Align 0x4000 (p_align=0x4000) for aarch64-linux-android.

[reez]

Looking for PR review and testing this from anyone but especially folks that would use on Android