feat: per-link path style toggle (bezier / smooth step)

backend/app/db/database.py

@@ -27,6 +27,8 @@ async def init_db() -> None:
             await conn.exec_driver_sql("ALTER TABLE nodes ADD COLUMN custom_colors JSON")
         with suppress(Exception):
             await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN custom_color TEXT")
+        with suppress(Exception):
+            await conn.exec_driver_sql("ALTER TABLE edges ADD COLUMN path_style TEXT")
 
 
 async def get_db():

backend/app/db/models.py

@@ -55,6 +55,7 @@ class Edge(Base):
     vlan_id: Mapped[int | None] = mapped_column(Integer)
     speed: Mapped[str | None] = mapped_column(String)
     custom_color: Mapped[str | None] = mapped_column(String)
+    path_style: Mapped[str | None] = mapped_column(String)
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)