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.

tests/unit/test_admin.py

@@ -81,6 +81,29 @@ async def test_admin_reads_and_updates_config(client):
     assert resp.json()["fee_address"] == "plm1qfeeaddress"
 
 
+async def test_admin_can_pause_and_resume_the_lottery(client):
+    headers = {"X-Admin-Token": "test-admin-token"}
+
+    resp = await client.get("/admin/config", headers=headers)
+    assert resp.json()["paused"] is False
+
+    resp = await client.post("/admin/pause", headers=headers)
+    assert resp.status_code == 200
+    assert resp.json()["paused"] is True
+
+    resp = await client.get("/admin/config", headers=headers)
+    assert resp.json()["paused"] is True
+
+    resp = await client.post("/admin/resume", headers=headers)
+    assert resp.status_code == 200
+    assert resp.json()["paused"] is False
+
+
+async def test_admin_pause_requires_token(client):
+    resp = await client.post("/admin/pause")
+    assert resp.status_code == 403
+
+
 async def test_admin_lists_users(client):
     from app.db import base as db_base
     from app.db.models import User

tests/unit/test_rounds_service.py

@@ -4,7 +4,7 @@ import pytest
 from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
 
 from app.db.base import Base
-from app.db.models import Round
+from app.db.models import Round, RoundConfig
 from app.rounds.service import get_active_round, open_new_round_if_needed
 
 ROUND_COOLDOWN_SECONDS = 30  # matches RoundConfig.round_cooldown_seconds' column default
@@ -81,3 +81,27 @@ async def test_opens_new_round_once_cooldown_elapses(session_factory):
     async with session_factory() as session:
         round_ = await open_new_round_if_needed(session)
         assert round_.status == "open"
+
+
+async def test_withholds_new_round_while_paused(session_factory):
+    stale_close = datetime.now(timezone.utc) - timedelta(seconds=ROUND_COOLDOWN_SECONDS + 1)
+    async with session_factory() as session:
+        session.add(Round(status="closed", closed_at=stale_close))
+        session.add(RoundConfig(fee_address="", paused=True))
+        await session.commit()
+
+    async with session_factory() as session:
+        round_ = await open_new_round_if_needed(session)
+        assert round_ is None
+
+
+async def test_pause_does_not_interrupt_a_round_in_progress(session_factory):
+    async with session_factory() as session:
+        session.add(Round(status="drawing"))
+        session.add(RoundConfig(fee_address="", paused=True))
+        await session.commit()
+
+    async with session_factory() as session:
+        returned = await open_new_round_if_needed(session)
+        assert returned is not None
+        assert returned.status == "drawing"