feat: display truncated lightning address for winners

- Add truncateLightningAddress utility (shows first 2 chars + ******)
- Backend: Include winner_address in past-wins API response
- Frontend: Display truncated address in past winners list
- Telegram: Add truncated address to draw announcements for transparency

Example: username@blink.sv -> us******@blink.sv

front_end/src/app/past-wins/page.tsx

@@ -13,6 +13,7 @@ interface PastWin {
   pot_total_sats: number;
   pot_after_fee_sats: number | null;
   winner_name: string;
+  winner_address: string | null;
   winning_ticket_serial: number | null;
 }
 
@@ -87,13 +88,19 @@ export default function PastWinsPage() {
                 </div>
               </div>
 
-              <div className="grid grid-cols-1 md:grid-cols-3 gap-4 text-sm">
+              <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-4 text-sm">
                 <div>
                   <div className="text-gray-400 mb-1">{STRINGS.pastWins.winner}</div>
                   <div className="text-white font-semibold">
                     {win.winner_name || 'Anon'}
                   </div>
                 </div>
+                <div>
+                  <div className="text-gray-400 mb-1">{STRINGS.pastWins.address}</div>
+                  <div className="text-white font-mono text-xs">
+                    {win.winner_address || 'N/A'}
+                  </div>
+                </div>
                 <div>
                   <div className="text-gray-400 mb-1">{STRINGS.pastWins.ticket}</div>
                   <div className="text-white">

front_end/src/constants/strings.ts

@@ -67,6 +67,7 @@ export const STRINGS = {
     description: 'Recent jackpots and their champions.',
     noWins: 'No completed jackpots yet. Check back soon!',
     winner: 'Winner',
+    address: 'Lightning Address',
     ticket: 'Ticket #',
     pot: 'Pot',
     drawTime: 'Draw Time',