Apply velvet-table redesign, fix game lifecycle and history bugs

Frontend:
- Dark green/gold "velvet table" visual redesign across the whole app
  (Auth, Lobby, GameList, GameTable, History, GameOver, modals), with
  Playfair Display/DM Sans typography and a centralized Tailwind palette.
- Desktop game table fit-scales to fill the window; mobile gets
  overlapping hand/trick layouts and larger touch-friendly cards.
- Standings sidebar now groups completed rounds by series with a
  per-series subtotal row, struck-through tips on missed bids.
- History page rewritten into a scoreboard-style detail view (player
  totals beside names, series grouped 2-up on desktop / stacked on
  mobile) and gained game names, completed/abandoned status, and a
  button to reopen a prematurely-ended game back into the lobby.

Backend:
- Fix started games being deleted from memory (and vanishing from
  everyone's lobby) when all players disconnect; only `end_game` tears
  down a started game now.
- Fix a crash writing a timezone-aware datetime into the naive
  `ended_at` Postgres column.
- Add `reopen_game`/`restore_game` to un-end a prematurely-ended game
  from history and resume it from the lobby.
- Let any seated player end an abandoned game once the host is
  offline, not just the host, so the game isn't stuck forever.
- Expose SERIES_PER_GAME/ROUNDS_PER_SERIES as named constants on the
  engine so the persistence layer derives game-completion rules from
  bridzik.py instead of re-encoding them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/components/GuessControls.tsx

@@ -17,8 +17,9 @@ export default function GuessControls({ cardsInRound, guesses, myOrder, activePl
 
   if (!isMyTurn) {
     return (
-      <p className="text-gray-400 text-sm text-center py-2">
-        Caka sa na tip: <span className="text-white font-semibold">{activePlayerName}</span>
+      <p className="text-center text-sm text-green-dim py-3">
+        Čaká sa na tip:{' '}
+        <span className="font-serif text-gold">{activePlayerName}</span>
       </p>
     );
   }
@@ -26,8 +27,8 @@ export default function GuessControls({ cardsInRound, guesses, myOrder, activePl
   const options = Array.from({ length: cardsInRound + 1 }, (_, i) => i);
 
   return (
-    <div className="flex flex-col items-center gap-2 py-2">
-      <p className="text-sm text-gray-300">Tvoj tip (pocet kopok):</p>
+    <div className="flex flex-col items-center gap-3 py-3">
+      <p className="font-serif italic text-gold-dim text-[14px]">Zadaj svoj tip (počet kopiek)</p>
       <div className="flex flex-wrap gap-2 justify-center">
         {options.map((n) => {
           const isForbidden = n === forbidden;
@@ -36,12 +37,12 @@ export default function GuessControls({ cardsInRound, guesses, myOrder, activePl
               key={n}
               disabled={isForbidden}
               onClick={() => emit.addGuess(n)}
-              title={isForbidden ? 'Zakázaná hodnota (suma = počet kopok)' : undefined}
+              title={isForbidden ? 'Zakázaná hodnota (súčet = počet kopiek)' : undefined}
               className={[
-                'w-10 h-10 rounded-lg font-bold text-lg border-2 transition-colors',
+                'w-11 h-11 rounded-full font-serif text-lg border-2 transition-colors',
                 isForbidden
-                  ? 'border-red-700 text-red-700 opacity-40 cursor-not-allowed'
-                  : 'border-blue-400 text-blue-200 hover:bg-blue-600 hover:border-blue-600 active:scale-95',
+                  ? 'border-[#5a2a2a] text-[#7a4040] opacity-40 cursor-not-allowed'
+                  : 'border-gold/50 text-gold hover:bg-gold hover:text-table hover:border-gold active:scale-95',
               ].join(' ')}
             >
               {n}