Restructure citizen vote page + add vote deadline

Reorganize the citizen page (/commune/[slug]) for voters: full-width
interactive chart with "Population" zoom by default, separate auth and
vote sections, countdown timer for vote deadline.

Backend: add vote_deadline column to communes with Alembic migration.
Admin: add deadline configuration card with datetime-local input.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/models/models.py

@@ -29,6 +29,7 @@ class Commune(Base):
     description = Column(Text, default="")
     is_active = Column(Boolean, default=True)
     created_at = Column(DateTime, default=datetime.utcnow)
+    vote_deadline = Column(DateTime, nullable=True)
 
     tariff_params = relationship("TariffParams", back_populates="commune", uselist=False)
     households = relationship("Household", back_populates="commune")

backend/app/routers/communes.py

@@ -67,6 +67,8 @@ async def update_commune(
         commune.description = data.description
     if data.is_active is not None:
         commune.is_active = data.is_active
+    if data.vote_deadline is not None:
+        commune.vote_deadline = data.vote_deadline
 
     await db.commit()
     await db.refresh(commune)

backend/app/schemas/schemas.py

@@ -35,6 +35,7 @@ class CommuneUpdate(BaseModel):
     name: str | None = None
     description: str | None = None
     is_active: bool | None = None
+    vote_deadline: datetime | None = None
 
 
 class CommuneOut(BaseModel):
@@ -44,6 +45,7 @@ class CommuneOut(BaseModel):
     description: str
     is_active: bool
     created_at: datetime
+    vote_deadline: datetime | None = None
 
     model_config = {"from_attributes": True}