Add a maintenance pause/resume switch and a proper user navbar

RoundConfig gets a paused flag toggled via new POST /admin/pause and
/admin/resume endpoints (audit-logged, surfaced as a "Manutenzione" card in
the admin Parametri view). Pausing only stops the *next* round from opening
once the current one closes — rounds/service.py:open_new_round_if_needed
still lets an in-progress round finish, draw, and pay out its winner
normally. GET /rounds/current exposes lottery_paused so the user page shows
a maintenance banner (even while logged out) instead of silently going idle.

Also replaces the user dashboard's stacked account-bar card + bento-grid
menu with a single sticky navbar (identity row + Deposito/Bet/Prelievo
tabs), and moves the page content into a dedicated .app-shell container so
the navbar itself can span full width.

app/api/routes/admin.py

@@ -29,6 +29,7 @@ _CONFIG_FIELDS = (
     "fee_rate_sat_vb",
     "rbf_timeout_seconds",
     "draw_animation_seconds",
+    "paused",
 )
 
 
@@ -41,6 +42,7 @@ class RoundConfigResponse(BaseModel):
     fee_rate_sat_vb: int
     rbf_timeout_seconds: int
     draw_animation_seconds: int
+    paused: bool
 
 
 class RoundConfigUpdate(BaseModel):
@@ -52,6 +54,7 @@ class RoundConfigUpdate(BaseModel):
     fee_rate_sat_vb: int | None = None
     rbf_timeout_seconds: int | None = None
     draw_animation_seconds: int | None = None
+    paused: bool | None = None
 
 
 def _config_response(config) -> RoundConfigResponse:
@@ -78,6 +81,27 @@ async def update_config(
     return _config_response(config)
 
 
+@router.post("/pause", response_model=RoundConfigResponse, dependencies=[Depends(require_admin)])
+async def pause_lottery(session: AsyncSession = Depends(get_session)) -> RoundConfigResponse:
+    """Maintenance switch: the round in progress (if any) still closes, draws,
+    and pays out its winner normally — only opening the *next* round is
+    suppressed until /admin/resume is called (rounds/service.py)."""
+    config = await get_round_config(session)
+    config.paused = True
+    await write_audit_log(session, "lottery_paused", {})
+    await session.commit()
+    return _config_response(config)
+
+
+@router.post("/resume", response_model=RoundConfigResponse, dependencies=[Depends(require_admin)])
+async def resume_lottery(session: AsyncSession = Depends(get_session)) -> RoundConfigResponse:
+    config = await get_round_config(session)
+    config.paused = False
+    await write_audit_log(session, "lottery_resumed", {})
+    await session.commit()
+    return _config_response(config)
+
+
 class AdminUserResponse(BaseModel):
     id: int
     username: str

app/api/routes/rounds.py

@@ -25,6 +25,7 @@ class CurrentRoundResponse(BaseModel):
     winner_user_id: int | None = None
     winner_amount_sats: int | None = None
     chain_tip_height: int | None = None
+    lottery_paused: bool = False
 
 
 @router.get("/current", response_model=CurrentRoundResponse)
@@ -39,6 +40,7 @@ async def current_round(request: Request, session: AsyncSession = Depends(get_se
             bet_amount_sats=config.bet_amount_sats,
             draw_animation_seconds=config.draw_animation_seconds,
             chain_tip_height=chain_tip_height,
+            lottery_paused=config.paused,
         )
 
     participant_count = await session.scalar(
@@ -60,4 +62,5 @@ async def current_round(request: Request, session: AsyncSession = Depends(get_se
         winner_user_id=round_.winner_user_id,
         winner_amount_sats=round_.winner_amount_sats,
         chain_tip_height=chain_tip_height,
+        lottery_paused=config.paused,
     )