fix: enable getrandom js feature for WASM compilation

The getrandom crate (transitive dep via rand/argon2) requires the
"js" feature flag to compile for wasm32-unknown-unknown targets.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/idfoto-wasm/Cargo.toml

@@ -15,6 +15,7 @@ serde_json = "1"
 hmac = "0.12"
 sha1 = "0.10"
 data-encoding = "2"
+getrandom = { version = "0.2", features = ["js"] }
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3"