feat: add PEZ presale system with wUSDT contribution

Implemented complete presale system for PEZ token distribution:

Backend (Pallet):
- Created pallet-presale at /home/mamostehp/Pezkuwi-SDK/pezkuwi/pallets/presale/
- Accepts wUSDT (Asset ID 2) contributions
- Tracks all contributors and amounts
- Distributes PEZ (Asset ID 1) after 45-day period
- Conversion rate: 1 wUSDT = 100 PEZ
- Includes emergency pause/unpause functionality
- Runtime integration documentation provided

Frontend:
- Created Presale page with contribution form
- Live stats: time remaining, total raised, contributors count
- Real-time balance display and conversion calculator
- Progress bar showing fundraising goal ($1M target)
- Added route /presale and navigation under Trading menu
- Connected to PolkadotContext and WalletContext

Technical Details:
- wUSDT: 6 decimals (Asset ID 2)
- PEZ: 12 decimals (Asset ID 1)
- Duration: 648,000 blocks (45 days @ 6s blocks)
- Treasury: PalletId "py/prsal"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/App.tsx

@@ -37,6 +37,7 @@ const Elections = lazy(() => import('./pages/Elections'));
 const EducationPlatform = lazy(() => import('./pages/EducationPlatform'));
 const P2PPlatform = lazy(() => import('./pages/P2PPlatform'));
 const DEXDashboard = lazy(() => import('./components/dex/DEXDashboard').then(m => ({ default: m.DEXDashboard })));
+const Presale = lazy(() => import('./pages/Presale'));
 const NotFound = lazy(() => import('@/pages/NotFound'));
 
 // Loading component
@@ -137,6 +138,7 @@ function App() {
                                   <DEXDashboard />
                                 </ProtectedRoute>
                               } />
+                              <Route path="/presale" element={<Presale />} />
                               <Route path="*" element={<NotFound />} />
                             </Routes>
                           </Suspense>