feat(identity-wallet): add get_stored_did_doc and get_device_key_id Tauri commands and IPC wrappers
- Adds get_stored_did_doc Rust command that retrieves the stored DID document
for a claimed identity and returns it as parsed JSON
- Adds get_device_key_id Rust command that retrieves the device key's did:key URI
for a claimed identity
- Registers both commands in tauri::generate_handler\![]
- Adds TypeScript wrappers in ipc.ts for both commands
- These commands support multi-identity display in IdentityListHome component
by providing DID document data and device key ID for rotation key status badges