feat: AI flow builder, visibility model, dashboard tabs, fork UI (#88)

- AI flow builder: scaffold → branch detail → assemble → review flow
- Generate All one-click branch generation with stop/cancel
- Regenerate scaffold suggestions button
- 3-action review screen: Start Flow, Open in Editor, Build Another
- Fix Publish button gated behind !isDirty
- Fix visibility column enforcement in tree access filter
- Add ?visibility filter and author_name to GET /trees
- Dashboard tabbed flows: My Flows / My Team / Public / All
- Create button in My Flows tab, window focus reload (stale data fix)
- Fork UI with optional reason modal
- Fix account_id nullability in User type and schema
- Keep is_public and visibility in sync on updates

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

frontend/src/components/ai-builder/AIFlowBuilderModal.tsx

@@ -37,6 +37,11 @@ export function AIFlowBuilderModal({ isOpen, onClose }: AIFlowBuilderModalProps)
   // Auto-trigger scaffold after conversation starts (ref prevents double-fire)
   const hasTriggeredScaffold = useRef(false)
   useEffect(() => {
+    // Reset guard when wizard resets to foundation (Start Over or close)
+    if (phase === 'foundation') {
+      hasTriggeredScaffold.current = false
+      return
+    }
     if (phase === 'scaffolding' && !hasTriggeredScaffold.current && !useAIFlowBuilderStore.getState().suggestedBranches.length) {
       hasTriggeredScaffold.current = true
       scaffold()
@@ -48,27 +53,48 @@ export function AIFlowBuilderModal({ isOpen, onClose }: AIFlowBuilderModalProps)
     onClose()
   }
 
-  const handleOpenInEditor = async () => {
-    if (!assembledTree) return
+  const createTree = async () => {
+    if (!assembledTree) return null
     try {
-      const tree = await treesApi.create({
+      return await treesApi.create({
         name: assembledTree.suggested_name,
         description: assembledTree.suggested_description,
         tree_structure: assembledTree.tree_structure,
         tree_type: metadata.flow_type,
         status: 'draft',
       })
-      handleClose()
-      const editorPath =
-        metadata.flow_type === 'procedural'
-          ? `/flows/${tree.id}/edit`
-          : `/trees/${tree.id}/edit`
-      navigate(editorPath)
     } catch {
       toast.error('Failed to create flow. Please try again.')
+      return null
     }
   }
 
+  const handleOpenInEditor = async () => {
+    const tree = await createTree()
+    if (!tree) return
+    handleClose()
+    const editorPath =
+      metadata.flow_type === 'procedural'
+        ? `/flows/${tree.id}/edit`
+        : `/trees/${tree.id}/edit`
+    navigate(editorPath)
+  }
+
+  const handleStartFlow = async () => {
+    const tree = await createTree()
+    if (!tree) return
+    handleClose()
+    const navigatePath =
+      metadata.flow_type === 'procedural'
+        ? `/flows/${tree.id}/navigate`
+        : `/trees/${tree.id}/navigate`
+    navigate(navigatePath)
+  }
+
+  const handleBuildAnother = () => {
+    reset()
+  }
+
   const getTitle = () => {
     switch (phase) {
       case 'foundation':
@@ -102,7 +128,11 @@ export function AIFlowBuilderModal({ isOpen, onClose }: AIFlowBuilderModalProps)
       {phase === 'generating' && <GeneratingAnimation />}
       {phase === 'detailing' && <BranchDetailView />}
       {phase === 'reviewing' && (
-        <TreePreviewCard onOpenInEditor={handleOpenInEditor} />
+        <TreePreviewCard
+          onOpenInEditor={handleOpenInEditor}
+          onStartFlow={handleStartFlow}
+          onBuildAnother={handleBuildAnother}
+        />
       )}
       {phase === 'error' && <ErrorView />}
     </Modal>