fix(krux): add Base43 decoding for encrypted QR codes

Implements support for Base43-encoded QR codes generated by Krux devices, resolving a bug where they were misidentified as invalid text.

- Adds a new `lib/base43.ts` module with a decoder ported from the official Krux Python implementation.
- Updates `detectEncryptionMode` to use the Base43 alphabet for more accurate `'krux'` format detection.
- Modifies `decryptFromKrux` to be robust, attempting to decode input as Hex first and falling back to Base43.
- This allows the Seed Blender to correctly parse and trigger the decryption flow for both Hex and Base43-encoded Krux QR codes.

src/lib/krux.ts

@@ -310,18 +310,34 @@ export async function encryptToKrux(params: {
   };
 }
 
+import { base43Decode } from './base43';
+
+// ... (rest of the file until decryptFromKrux)
+
 /**
- * Decrypt KEF hex to mnemonic
+ * Decrypt KEF data (Hex or Base43) to mnemonic
  */
 export async function decryptFromKrux(params: {
-  kefHex: string;
+  kefData: string;
   passphrase: string;
 }): Promise<{ mnemonic: string; label: string; version: number; iterations: number }> {
   if (!params.passphrase) {
     throw new Error("Passphrase is required for Krux decryption");
   }
   
-  const bytes = hexToBytes(params.kefHex);
+  let bytes: Uint8Array;
+  try {
+      // First, try to decode as hex
+      bytes = hexToBytes(params.kefData);
+  } catch (e) {
+      // If hex fails, try to decode as Base43
+      try {
+          bytes = base43Decode(params.kefData);
+      } catch (e2) {
+          throw new Error("Invalid Krux data: Not a valid Hex or Base43 string.");
+      }
+  }
+
   const { label, version, iterations, payload } = unwrap(bytes);
   const cipher = new KruxCipher(params.passphrase, label, iterations);
   const decrypted = await cipher.decrypt(payload, version);