feat(blender): add Seed Blender feature

Implements a new 'Seed Blender' feature that allows users to securely combine multiple BIP39 mnemonics and enhance them with dice roll entropy.

- Adds a new 'Seed Blender' tab to the main UI.
- Implements a multi-step workflow for inputting mnemonics (manual/QR) and dice rolls.
- Provides live validation and previews for blended seeds and dice-only entropy.
- Includes statistical analysis of dice rolls (chi-square, distribution) and pattern detection for quality assessment.
- The core logic is a 1-to-1 port of the reference Python implementation, using the Web Crypto API for browser compatibility and Node.js for testing.
- A full suite of unit tests ported from the reference implementation ensures correctness and deterministic outputs.

src/components/Header.tsx

@@ -25,8 +25,8 @@ interface HeaderProps {
   sessionItems: StorageItem[];
   events: ClipboardEvent[];
   onOpenClipboardModal: () => void;
-  activeTab: 'backup' | 'restore';
-  setActiveTab: (tab: 'backup' | 'restore') => void;
+  activeTab: 'backup' | 'restore' | 'seedblender';
+  setActiveTab: (tab: 'backup' | 'restore' | 'seedblender') => void;
   encryptedMnemonicCache: any;
   handleLockAndClear: () => void;
   appVersion: string;
@@ -101,6 +101,12 @@ const Header: React.FC<HeaderProps> = ({
             >
               Restore
             </button>
+            <button 
+              className={`px-4 py-2 rounded-lg ${activeTab === 'seedblender' ? 'bg-teal-500 hover:bg-teal-600' : 'bg-slate-700 hover:bg-slate-600'}`}
+              onClick={() => setActiveTab('seedblender')}
+            >
+              Seed Blender
+            </button>
           </div>
         </div>