feat: customizable link color per edge

- Add custom_color field to EdgeData type, Edge DB model and all schemas
- HomelableEdge applies custom_color as stroke override (before selected highlight)
- EDGE_DEFAULT_COLORS extracted to utils/edgeColors.ts (react-refresh compliant)
- EdgeModal: color picker row showing effective color (custom or type default)
  with hex value, Reset button when custom color is active
- Auto-migration adds custom_color column to edges table

backend/app/db/database.py

@@ -25,6 +25,8 @@ async def init_db() -> None:
             await conn.exec_driver_sql("ALTER TABLE nodes ADD COLUMN container_mode BOOLEAN NOT NULL DEFAULT 0")
         with suppress(Exception):
             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")
 
 
 async def get_db():

backend/app/db/models.py

@@ -54,6 +54,7 @@ class Edge(Base):
     label: Mapped[str | None] = mapped_column(String)
     vlan_id: Mapped[int | None] = mapped_column(Integer)
     speed: Mapped[str | None] = mapped_column(String)
+    custom_color: Mapped[str | None] = mapped_column(String)
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=_now)
 
 

backend/app/schemas/canvas.py

@@ -34,6 +34,7 @@ class EdgeSave(BaseModel):
     label: str | None = None
     vlan_id: int | None = None
     speed: str | None = None
+    custom_color: str | None = None
 
 
 class CanvasSaveRequest(BaseModel):

backend/app/schemas/edges.py

@@ -10,6 +10,7 @@ class EdgeBase(BaseModel):
     label: str | None = None
     vlan_id: int | None = None
     speed: str | None = None
+    custom_color: str | None = None
 
 
 class EdgeCreate(EdgeBase):
@@ -21,6 +22,7 @@ class EdgeUpdate(BaseModel):
     label: str | None = None
     vlan_id: int | None = None
     speed: str | None = None
+    custom_color: str | None = None
 
 
 class EdgeResponse(EdgeBase):