feat: allow interfaces to have no zone (shorewall '-' zone)

backend/app/models.py

@@ -59,11 +59,11 @@ class Interface(Base):
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     config_id: Mapped[int] = mapped_column(Integer, ForeignKey("configs.id"), nullable=False)
     name: Mapped[str] = mapped_column(String(32), nullable=False)
-    zone_id: Mapped[int] = mapped_column(Integer, ForeignKey("zones.id"), nullable=False)
+    zone_id: Mapped[int | None] = mapped_column(Integer, ForeignKey("zones.id"), nullable=True)
     options: Mapped[str] = mapped_column(Text, default="")
 
     config: Mapped["Config"] = relationship("Config", back_populates="interfaces")
-    zone: Mapped["Zone"] = relationship("Zone", back_populates="interfaces")
+    zone: Mapped["Zone | None"] = relationship("Zone", back_populates="interfaces")
 
 
 class Policy(Base):

backend/app/schemas.py

@@ -64,7 +64,7 @@ class ZoneOut(BaseModel):
 # --- Interface ---
 class InterfaceCreate(BaseModel):
     name: str
-    zone_id: int
+    zone_id: Optional[int] = None
     options: str = ""
 
 
@@ -78,7 +78,7 @@ class InterfaceOut(BaseModel):
     id: int
     config_id: int
     name: str
-    zone_id: int
+    zone_id: Optional[int]
     options: str
 
     model_config = {"from_attributes": True}

backend/app/shorewall_generator.py

@@ -28,7 +28,8 @@ class ShorewallGenerator:
     def interfaces(self) -> str:
         lines = [self._header("interfaces"), "#ZONE".ljust(16) + "INTERFACE".ljust(16) + "OPTIONS\n"]
         for iface in self._config.interfaces:
-            lines.append(self._col(iface.zone.name, iface.name, iface.options or "-"))
+            zone = iface.zone.name if iface.zone else "-"
+            lines.append(self._col(zone, iface.name, iface.options or "-"))
         return "".join(lines)
 
     def policy(self) -> str: