Add ExifTool worker and Pinia store for off-thread metadata reads.

Warm up WASM in a dedicated worker with a tiny JPEG probe and expose init/read RPC to the main thread.

frontend/src/utils/base64ToBytes.ts

@@ -0,0 +1,10 @@
+export function base64ToBytes(base64: string): Uint8Array {
+    const binary = atob(base64);
+    const bytes = new Uint8Array(binary.length);
+
+    for (let i = 0; i < binary.length; i++) {
+        bytes[i] = binary.charCodeAt(i);
+    }
+
+    return bytes;
+}