Fix sprint timezone bug and add auto-rollover

- Sprint end dates now treated as end-of-day (23:59:59) to handle timezone issues
  where sprints appeared empty before local midnight
- Added auto-rollover: when a sprint ends, incomplete tasks automatically
  move to the next sprint, ended sprint marked as completed
- Applied fix to both main page and BacklogView

src/app/page.tsx

@@ -359,6 +359,7 @@ export default function Home() {
     setCurrentUser,
     syncFromServer,
     isLoading,
+    updateSprint,
   } = useTaskStore()
 
   const [newTaskOpen, setNewTaskOpen] = useState(false)
@@ -583,12 +584,14 @@ export default function Home() {
   }, [selectedTask])
 
   // Get current active sprint (across all projects)
+  // Treat end date as end-of-day (23:59:59) to handle timezone issues
   const now = new Date()
-  const currentSprint = sprints.find((s) => 
-    s.status === 'active' &&
-    new Date(s.startDate) <= now &&
-    new Date(s.endDate) >= now
-  )
+  const currentSprint = sprints.find((s) => {
+    if (s.status !== 'active') return false
+    const sprintEnd = new Date(s.endDate)
+    sprintEnd.setHours(23, 59, 59, 999)
+    return new Date(s.startDate) <= now && sprintEnd >= now
+  })
   
   // Filter tasks to only show current sprint tasks in Kanban (from ALL projects)
   const sprintTasks = currentSprint
@@ -604,6 +607,51 @@ export default function Home() {
         return true
       })
     : []
+
+  // Auto-rollover: Move incomplete tasks from ended sprints to next sprint
+  useEffect(() => {
+    if (!authReady || sprints.length === 0) return
+
+    const now = new Date()
+    const endedSprints = sprints.filter((s) => {
+      if (s.status !== 'active') return false
+      const sprintEnd = new Date(s.endDate)
+      sprintEnd.setHours(23, 59, 59, 999)
+      return sprintEnd < now
+    })
+
+    if (endedSprints.length === 0) return
+
+    // Find next sprint (earliest start date that's in the future or active)
+    const nextSprint = sprints
+      .filter((s) => s.status === 'planning' || (s.status === 'active' && !endedSprints.find((e) => e.id === s.id)))
+      .sort((a, b) => new Date(a.startDate).getTime() - new Date(b.startDate).getTime())[0]
+
+    if (!nextSprint) return
+
+    // Process each ended sprint
+    endedSprints.forEach((endedSprint) => {
+      const incompleteTasks = tasks.filter(
+        (t) => t.sprintId === endedSprint.id && t.status !== 'done' && t.status !== 'canceled' && t.status !== 'archived'
+      )
+
+      if (incompleteTasks.length > 0) {
+        console.log(`Auto-rolling over ${incompleteTasks.length} tasks from "${endedSprint.name}" to "${nextSprint.name}"`)
+
+        // Move incomplete tasks to next sprint
+        incompleteTasks.forEach((task) => {
+          updateTask(task.id, { sprintId: nextSprint.id })
+        })
+
+        // Mark ended sprint as completed
+        updateSprint(endedSprint.id, { status: 'completed' })
+      } else {
+        // No incomplete tasks, just mark as completed
+        updateSprint(endedSprint.id, { status: 'completed' })
+      }
+    })
+  }, [authReady, sprints, tasks, updateTask, updateSprint])
+
   const activeKanbanTask = activeKanbanTaskId
     ? sprintTasks.find((task) => task.id === activeKanbanTaskId)
     : null

src/components/BacklogView.tsx

@@ -306,13 +306,14 @@ export function BacklogView({ searchQuery = "" }: BacklogViewProps) {
   )
 
   // Get current active sprint
+  // Treat end date as end-of-day (23:59:59) to handle timezone issues
   const now = new Date()
-  const currentSprint = sprints.find(
-    (s) =>
-      s.status === "active" &&
-      new Date(s.startDate) <= now &&
-      new Date(s.endDate) >= now
-  )
+  const currentSprint = sprints.find((s) => {
+    if (s.status !== "active") return false
+    const sprintEnd = new Date(s.endDate)
+    sprintEnd.setHours(23, 59, 59, 999)
+    return new Date(s.startDate) <= now && sprintEnd >= now
+  })
 
   // Get other sprints (not current)
   const otherSprints = sprints.filter((s) => s.id !== currentSprint?.id)