fix: network diagram team_id guard + multi-style edge routing

Backend:
- Guard create_diagram with 422 if current_user.team_id is None (prevents
  NOT NULL constraint crash for accounts not yet assigned to a team)
- Add routing field to DiagramEdge schema (straight/curved/step)

Frontend:
- ConnectionEdge now supports straight (default), curved (bezier), and
  step (smooth-step) routing per-edge via routing field in edge data
- PropertiesPanel Connection section gets a Line Style toggle:
  Straight | Curved | Step buttons, active state highlights in accent
- handleEdgeUpdate and serializeEdges now propagate the routing field
- DiagramEdge type gets optional routing field

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

backend/app/api/endpoints/network_diagrams.py

@@ -130,6 +130,11 @@ async def create_diagram(
     db: Annotated[AsyncSession, Depends(get_db)],
     current_user: Annotated[User, Depends(get_current_active_user)],
 ) -> NetworkDiagramResponse:
+    if current_user.team_id is None:
+        raise HTTPException(
+            status_code=422,
+            detail="Network Diagrams require a team account. Assign your account to a team first.",
+        )
     diagram = NetworkDiagram(
         team_id=current_user.team_id,
         name=data.name,

backend/app/schemas/network_diagram.py

@@ -38,6 +38,7 @@ class DiagramEdge(BaseModel):
     connectionType: str = "ethernet"
     speed: str | None = None
     notes: str | None = None
+    routing: str | None = None
 
 
 class NetworkDiagramCreate(BaseModel):

frontend/src/components/network/edges/ConnectionEdge.tsx

@@ -1,8 +1,9 @@
 import { memo } from 'react'
-import { BaseEdge, EdgeLabelRenderer, getStraightPath, type EdgeProps } from '@xyflow/react'
+import { BaseEdge, EdgeLabelRenderer, getStraightPath, getBezierPath, getSmoothStepPath, type EdgeProps } from '@xyflow/react'
 
 interface ConnectionEdgeData {
   connectionType?: string
+  routing?: string | null
   speed?: string | null
   notes?: string | null
   [key: string]: unknown
@@ -19,17 +20,26 @@ const CONNECTION_STYLES: Record<string, { stroke: string; strokeDasharray?: stri
 
 const DEFAULT_STYLE = { stroke: '#848b9b', strokeWidth: 2 }
 
+function getEdgePath(routing: string | null | undefined, props: EdgeProps) {
+  const base = {
+    sourceX: props.sourceX,
+    sourceY: props.sourceY,
+    sourcePosition: props.sourcePosition,
+    targetX: props.targetX,
+    targetY: props.targetY,
+    targetPosition: props.targetPosition,
+  }
+  if (routing === 'curved') return getBezierPath(base)
+  if (routing === 'step') return getSmoothStepPath(base)
+  return getStraightPath(base)
+}
+
 function ConnectionEdgeComponent(props: EdgeProps) {
   const edgeData = props.data as ConnectionEdgeData | undefined
   const connectionType = edgeData?.connectionType || 'ethernet'
   const style = CONNECTION_STYLES[connectionType] || DEFAULT_STYLE
 
-  const [edgePath, labelX, labelY] = getStraightPath({
-    sourceX: props.sourceX,
-    sourceY: props.sourceY,
-    targetX: props.targetX,
-    targetY: props.targetY,
-  })
+  const [edgePath, labelX, labelY] = getEdgePath(edgeData?.routing, props)
 
   return (
     <>

frontend/src/components/network/panels/PropertiesPanel.tsx

@@ -1,5 +1,5 @@
 import { useCallback } from 'react'
-import { Trash2 } from 'lucide-react'
+import { Trash2, Minus, Spline, GitBranch } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import type { DeviceProperties, DiagramEdge } from '@/types'
 import type { Node, Edge } from '@xyflow/react'
@@ -139,6 +139,35 @@ export function PropertiesPanel({
               mono
             />
           </div>
+          <div className="flex flex-col gap-1">
+            <FieldLabel>Line Style</FieldLabel>
+            <div className="flex gap-1">
+              {([
+                { value: null, icon: Minus, label: 'Straight' },
+                { value: 'curved', icon: Spline, label: 'Curved' },
+                { value: 'step', icon: GitBranch, label: 'Step' },
+              ] as const).map(({ value, icon: Icon, label }) => {
+                const routing = (edgeData.routing as string | null | undefined) ?? null
+                const active = routing === value
+                return (
+                  <button
+                    key={label}
+                    title={label}
+                    onClick={() => onEdgeUpdate(selectedEdge.id, { routing: value })}
+                    className={cn(
+                      'flex flex-1 items-center justify-center gap-1 rounded border py-1.5 text-[10px] transition-colors',
+                      active
+                        ? 'border-accent bg-accent/10 text-accent'
+                        : 'border-default text-muted-foreground hover:border-hover hover:text-primary',
+                    )}
+                  >
+                    <Icon size={12} />
+                    {label}
+                  </button>
+                )
+              })}
+            </div>
+          </div>
           <div className="flex items-center justify-between">
             <FieldLabel>Show Traffic</FieldLabel>
             <button

frontend/src/pages/NetworkDiagrams/DiagramEditor.tsx

@@ -151,6 +151,7 @@ function DiagramEditorInner() {
               connectionType: e.connectionType,
               speed: e.speed,
               notes: e.notes,
+              routing: e.routing ?? null,
             },
           }))
         )
@@ -193,15 +194,19 @@ function DiagramEditorInner() {
   }, [getNodes])
 
   const serializeEdges = useCallback((): DiagramEdge[] => {
-    return edges.map(e => ({
-      id: e.id,
-      source: e.source,
-      target: e.target,
-      label: (e.label as string) || null,
-      connectionType: (e.data as Record<string, unknown>)?.connectionType as string || 'ethernet',
-      speed: (e.data as Record<string, unknown>)?.speed as string || null,
-      notes: (e.data as Record<string, unknown>)?.notes as string || null,
-    }))
+    return edges.map(e => {
+      const d = (e.data as Record<string, unknown>) || {}
+      return {
+        id: e.id,
+        source: e.source,
+        target: e.target,
+        label: (e.label as string) || null,
+        connectionType: d.connectionType as string || 'ethernet',
+        speed: d.speed as string || null,
+        notes: d.notes as string || null,
+        routing: d.routing as string || null,
+      }
+    })
   }, [edges])
 
   const handleSave = useCallback(async () => {
@@ -363,6 +368,7 @@ function DiagramEditorInner() {
           ...(updates.connectionType !== undefined ? { connectionType: updates.connectionType } : {}),
           ...(updates.speed !== undefined ? { speed: updates.speed } : {}),
           ...(updates.notes !== undefined ? { notes: updates.notes } : {}),
+          ...(updates.routing !== undefined ? { routing: updates.routing } : {}),
         },
       }
     }))

frontend/src/types/network-diagram.ts

@@ -28,6 +28,7 @@ export interface DiagramEdge {
   connectionType: string
   speed: string | null
   notes: string | null
+  routing?: string | null
 }
 
 export interface DeviceTypeResponse {