build(ext): align wasm.d.ts with relicario-wasm surface

Add initSync named export (Chrome MV3 service worker path — can't use
dynamic import()), and correct TotpCode.expires_at from number to bigint
to match the u64 wasm-bindgen output.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/src/wasm.d.ts

@@ -15,7 +15,7 @@ export class EncryptedAttachment {
 
 export class TotpCode {
   readonly code: string;
-  readonly expires_at: number;
+  readonly expires_at: bigint;
   free(): void;
 }
 
@@ -56,3 +56,6 @@ export function totp_compute(config_json: string, now_unix_seconds: bigint): Tot
 
 // Initializer (wasm-bindgen's default init function).
 export default function init(module_or_path?: unknown): Promise<void>;
+
+// wasm-bindgen's sync init — Chrome MV3 service workers can't use dynamic import().
+export function initSync(args: { module: WebAssembly.Module }): void;