fix(platform-wallet): check C enum values at the FFI boundary #5741

Problem

rs-platform-wallet-ffi exports take FFINetwork by value: 30 on v5.1-dev, 36 once #5727 lands. FFINetwork is a #[repr(C)] Rust enum with discriminants 0 to 3. A C caller that passes any other integer creates an invalid Rust enum value on entry, which is undefined behaviour before network.into() runs. The Swift wrappers and the JNI net_from_ord helper only produce valid values today, so this is hardening of the public C boundary, not a failure seen in the shipped wrappers.

#5727 already does this for the mnemonic language: platform_wallet_mnemonic_generate and platform_wallet_mnemonic_word_list take a u32 and convert it with TryFrom<u32> for FFIMnemonicLanguage, returning ErrorInvalidParameter for an unknown value, and cbindgen still exports the enum as the list of valid values.

Proposed direction

Apply the same pattern to every C enum parameter in the crate, starting with the network:

• Take the network as u32 and convert it with one checked TryFrom<u32>, returning ErrorInvalidParameter on an unknown value.
• Keep exporting the enum in the header so hosts still have the named values.
• Update the Swift and Kotlin call sites to pass the raw value.
• Test an out-of-range integer at each converted entry point without ever building an invalid enum value in Rust.

This changes the C signatures of every affected export, so it belongs in one coordinated change rather than per function. Once #5728 moves FFINetwork into rs-sdk-ffi, the conversion can live next to the type.