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.

migrations/versions/5f2079b95b33_add_paused_to_round_config.py

@@ -0,0 +1,37 @@
+"""add paused to round_config
+
+Revision ID: 5f2079b95b33
+Revises: 1db52f3a7c67
+Create Date: 2026-07-22 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '5f2079b95b33'
+down_revision: Union[str, Sequence[str], None] = '1db52f3a7c67'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    # server_default backfills the existing singleton row (if any); dropped right
+    # after so new rows go through the ORM default instead of a stale constant.
+    op.add_column(
+        'round_config', sa.Column('paused', sa.Boolean(), nullable=False, server_default=sa.false())
+    )
+    with op.batch_alter_table('round_config') as batch_op:
+        batch_op.alter_column('paused', server_default=None)
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('round_config', 'paused')
+    # ### end Alembic commands ###