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/components/SeedBlender.tsx

@@ -174,7 +174,7 @@ export function SeedBlender({ onDirtyStateChange, setMnemonicForBackup, requestT
     try {
         let mnemonic: string;
         if (entry.inputType === 'krux') {
-            mnemonic = (await decryptFromKrux({ kefHex: entry.rawInput, passphrase: entry.passwordInput })).mnemonic;
+            mnemonic = (await decryptFromKrux({ kefData: entry.rawInput, passphrase: entry.passwordInput })).mnemonic;
         } else { // seedpgp
             mnemonic = (await decryptFromSeed({ frameText: entry.rawInput, messagePassword: entry.passwordInput, mode: 'pgp' })).w;
         }