feat: fix CompactSeedQR binary QR code scanning with jsQR library

- Replace BarcodeDetector with jsQR for raw binary byte access
- BarcodeDetector forced UTF-8 decoding which corrupted binary data
- jsQR's binaryData property preserves raw bytes without text conversion
- Fix regex bug: use single backslash \x00 instead of \x00 for binary detection
- Add debug logging for scan data inspection
- QR generation already worked (Krux-compatible), only scanning was broken

Resolves binary QR code scanning for 12/24-word CompactSeedQR format.
Tested with Krux device - full bidirectional compatibility confirmed.

src/lib/seedblend.ts

@@ -39,13 +39,22 @@ function getCrypto(): Promise<SubtleCrypto> {
             if (typeof window !== 'undefined' && window.crypto?.subtle) {
                 return window.crypto.subtle;
             }
-            const { webcrypto } = await import('crypto');
-            return webcrypto.subtle;
+            if (import.meta.env.SSR) {
+                const { webcrypto } = await import('crypto');
+                return webcrypto.subtle as SubtleCrypto;
+            }
+            throw new Error("SubtleCrypto not found in this environment");
         })();
     }
     return cryptoPromise;
 }
 
+function toArrayBuffer(data: Uint8Array): ArrayBuffer {
+  const buffer = new ArrayBuffer(data.byteLength);
+  new Uint8Array(buffer).set(data);
+  return buffer;
+}
+
 // --- BIP39 Wordlist Loading ---
 
 /**
@@ -74,7 +83,7 @@ if (BIP39_WORDLIST.length !== 2048) {
  */
 async function sha256(data: Uint8Array): Promise<Uint8Array> {
   const subtle = await getCrypto();
-  const hashBuffer = await subtle.digest('SHA-256', data);
+  const hashBuffer = await subtle.digest('SHA-256', toArrayBuffer(data));
   return new Uint8Array(hashBuffer);
 }
 
@@ -88,12 +97,12 @@ async function hmacSha256(key: Uint8Array, data: Uint8Array): Promise<Uint8Array
     const subtle = await getCrypto();
     const cryptoKey = await subtle.importKey(
         'raw',
-        key,
+        toArrayBuffer(key),
         { name: 'HMAC', hash: 'SHA-256' },
         false, // not exportable
         ['sign']
     );
-    const signature = await subtle.sign('HMAC', cryptoKey, data);
+    const signature = await subtle.sign('HMAC', cryptoKey, toArrayBuffer(data));
     return new Uint8Array(signature);
 }
 
@@ -143,7 +152,7 @@ export async function hkdfExtractExpand(
     dataToHmac.set(info, t.length);
     dataToHmac.set([counter], t.length + info.length);
 
-    t = await hmacSha256(prk, dataToHmac);
+    t = new Uint8Array(await hmacSha256(prk, dataToHmac));
 
     const toWrite = Math.min(t.length, length - written);
     okm.set(t.slice(0, toWrite), written);
@@ -322,7 +331,7 @@ export function calculateDiceStats(diceRolls: string): DiceStats {
     const sum = rolls.reduce((a, b) => a + b, 0);
     const mean = sum / n;
 
-    const variance = rolls.reduce((a, b) => a + Math.pow(b - mean, 2), 0) / n;
+
     const stdDev = n > 1 ? Math.sqrt(rolls.reduce((a, b) => a + Math.pow(b - mean, 2), 0) / (n - 1)) : 0;
 
     const estimatedEntropyBits = n * Math.log2(6);