feat: inline edit for patterns in library (name, description, category, direction, regime)

- Backend: PATCH /api/patterns/custom/{id} — partial update, only provided fields changed
- useApi.ts: usePatchPattern mutation hook
- PatternCard: pencil icon (non-builtin only) → edit mode with inline inputs for name, description, direction (select), category, and #regime; ✓/✗ buttons to save or cancel; card border highlights blue while editing

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

frontend/src/hooks/useApi.ts

@@ -311,6 +311,21 @@ export const useDeletePattern = () => {
   })
 }
 
+export const usePatchPattern = () => {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: (body: {
+      id: string
+      name?: string
+      description?: string
+      category?: string
+      signal_direction?: string
+      regime_tag?: string
+    }) => api.patch(`/patterns/custom/${body.id}`, body).then(r => r.data),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['all-patterns'] }),
+  })
+}
+
 export const useTogglePattern = () => {
   const qc = useQueryClient()
   return useMutation({