feat: add Basic animation type for edges

Adds a new "basic" animation mode that uses React Flow's native animated
dashes — the entire stroke moves as dashes, with no solid line underneath.
Distinct from "snake" (moving dot) and "flow" (overlay on solid line).

- Frontend: new Basic button in EdgeModal, animMode mapping, passes
  animated={true} to BaseEdge when mode is "basic"
- Backend: normalize_animated accepts "basic" as a valid value
- Tests: EdgeModal + canvas round-trip tests for basic mode

frontend/src/components/canvas/edges/index.tsx

@@ -233,9 +233,10 @@ export function HomelableEdge({ id, source, target, sourceX, sourceY, targetX, t
     ...(selected ? { stroke: theme.colors.edgeSelectedColor, filter: `drop-shadow(0 0 4px ${theme.colors.edgeSelectedColor}88)` } : {}),
   }
 
-  const animMode: 'none' | 'snake' | 'flow' =
+  const animMode: 'none' | 'snake' | 'flow' | 'basic' =
     data?.animated === true || data?.animated === 'snake' ? 'snake' :
-    data?.animated === 'flow' ? 'flow' : 'none'
+    data?.animated === 'flow' ? 'flow' :
+    data?.animated === 'basic' ? 'basic' : 'none'
 
   const animColor = customColor ?? (edgeType === 'vlan' ? getVlanColor(data?.vlan_id as number | undefined) : edgeColors[edgeType as keyof typeof edgeColors] as string)
 
@@ -245,7 +246,7 @@ export function HomelableEdge({ id, source, target, sourceX, sourceY, targetX, t
 
   return (
     <>
-      <BaseEdge id={id} path={edgePath} style={style} interactionWidth={16} />
+      <BaseEdge id={id} path={edgePath} style={style} interactionWidth={16} animated={animMode === 'basic'} />
 
       {animMode === 'snake' && (
         <path

frontend/src/components/modals/EdgeModal.tsx

@@ -10,11 +10,12 @@ import { EDGE_DEFAULT_COLORS } from '@/utils/edgeColors'
 
 const EDGE_TYPES = Object.entries(EDGE_TYPE_LABELS) as [EdgeType, string][]
 
-type AnimMode = 'none' | 'snake' | 'flow'
+type AnimMode = 'none' | 'basic' | 'snake' | 'flow'
 
 function toAnimMode(v: EdgeData['animated']): AnimMode {
   if (v === true || v === 'snake') return 'snake'
   if (v === 'flow') return 'flow'
+  if (v === 'basic') return 'basic'
   return 'none'
 }
 
@@ -127,7 +128,7 @@ export function EdgeModal({ open, onClose, onSubmit, onDelete, onClearWaypoints,
           <div className="flex flex-col gap-1.5">
             <Label className="text-xs text-muted-foreground">Animation</Label>
             <div className="flex rounded-md overflow-hidden border border-[#30363d]">
-              {(['none', 'snake', 'flow'] as AnimMode[]).map((mode, i) => (
+              {(['none', 'basic', 'snake', 'flow'] as AnimMode[]).map((mode, i) => (
                 <button
                   key={mode}
                   type="button"
@@ -136,10 +137,10 @@ export function EdgeModal({ open, onClose, onSubmit, onDelete, onClearWaypoints,
                   style={{
                     background: animation === mode ? '#00d4ff22' : '#21262d',
                     color: animation === mode ? '#00d4ff' : '#8b949e',
-                    borderRight: i < 2 ? '1px solid #30363d' : undefined,
+                    borderRight: i < 3 ? '1px solid #30363d' : undefined,
                   }}
                 >
-                  {mode === 'none' ? 'None' : mode === 'snake' ? 'Snake' : 'Flow'}
+                  {mode === 'none' ? 'None' : mode === 'basic' ? 'Basic' : mode === 'snake' ? 'Snake' : 'Flow'}
                 </button>
               ))}
             </div>

frontend/src/components/modals/__tests__/EdgeModal.test.tsx

@@ -122,6 +122,21 @@ describe('EdgeModal', () => {
     expect(onSubmit.mock.calls[0][0].animated).toBe('flow')
   })
 
+  it('selecting Basic sends animated: "basic"', () => {
+    const onSubmit = vi.fn()
+    render(<EdgeModal open onClose={vi.fn()} onSubmit={onSubmit} />)
+    fireEvent.click(screen.getByText('Basic'))
+    fireEvent.click(screen.getByRole('button', { name: 'Connect' }))
+    expect(onSubmit.mock.calls[0][0].animated).toBe('basic')
+  })
+
+  it('pre-fills animation from initial "basic" string', () => {
+    const onSubmit = vi.fn()
+    render(<EdgeModal open onClose={vi.fn()} onSubmit={onSubmit} initial={{ animated: 'basic' }} />)
+    fireEvent.click(screen.getByRole('button', { name: 'Connect' }))
+    expect(onSubmit.mock.calls[0][0].animated).toBe('basic')
+  })
+
   it('selecting None after Snake omits animated from payload', () => {
     const onSubmit = vi.fn()
     render(<EdgeModal open onClose={vi.fn()} onSubmit={onSubmit} />)