Add draw_animation_seconds config and expose winner info during a round

RoundConfig gains draw_animation_seconds (default 20) — the minimum
time the frontend's "estrazione in corso" animation plays before
revealing a winner. It's purely a UI cue: the real draw still waits for
a confirmed block for its entropy (rounds/scheduler.py), which usually
takes much longer than this value, so it only ever extends the
animation, never truncates the real wait.

GET /rounds/current now also returns draw_animation_seconds,
winner_user_id and winner_amount_sats (all populated once the
scheduler sets them on the round, i.e. from "paying_out" onward) so a
client can determine and reveal the outcome. GET /users/me now returns
the user's own id, needed client-side to compare against winner_user_id.

Admin config CRUD refactored to a shared field tuple (_CONFIG_FIELDS)
instead of repeating the same 7-then-8 field list three times.

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

app/api/routes/rounds.py

@@ -21,6 +21,9 @@ class CurrentRoundResponse(BaseModel):
     participant_count: int = 0
     bet_amount_sats: int
     jackpot_sats: int = 0
+    draw_animation_seconds: int
+    winner_user_id: int | None = None
+    winner_amount_sats: int | None = None
 
 
 @router.get("/current", response_model=CurrentRoundResponse)
@@ -29,7 +32,9 @@ async def current_round(session: AsyncSession = Depends(get_session)) -> Current
     round_ = await get_active_round(session)
     if round_ is None:
         await session.commit()
-        return CurrentRoundResponse(bet_amount_sats=config.bet_amount_sats)
+        return CurrentRoundResponse(
+            bet_amount_sats=config.bet_amount_sats, draw_animation_seconds=config.draw_animation_seconds
+        )
 
     participant_count = await session.scalar(
         select(func.count()).select_from(RoundParticipant).where(RoundParticipant.round_id == round_.id)
@@ -46,4 +51,7 @@ async def current_round(session: AsyncSession = Depends(get_session)) -> Current
         participant_count=participant_count,
         bet_amount_sats=config.bet_amount_sats,
         jackpot_sats=participant_count * config.bet_amount_sats,
+        draw_animation_seconds=config.draw_animation_seconds,
+        winner_user_id=round_.winner_user_id,
+        winner_amount_sats=round_.winner_amount_sats,
     )