feat: refactor dual-track architecture (Phase 1-5)

## Backend Changes
- **Service Layer Refactoring**:
  - Add ProcessingOrchestrator for unified document processing
  - Add PDFTableRenderer for table rendering extraction
  - Add PDFFontManager for font management with CJK support
  - Add MemoryPolicyEngine (73% code reduction from MemoryGuard)

- **Bug Fixes**:
  - Fix Direct Track table row span calculation
  - Fix OCR Track image path handling
  - Add cell_boxes coordinate validation
  - Filter out small decorative images
  - Add covering image detection

## Frontend Changes
- **State Management**:
  - Add TaskStore for centralized task state management
  - Add localStorage persistence for recent tasks
  - Add processing state tracking

- **Type Consolidation**:
  - Merge shared types from api.ts to apiV2.ts
  - Update imports in authStore, uploadStore, ResultsTable, SettingsPage

- **Page Integration**:
  - Integrate TaskStore in ProcessingPage and TaskDetailPage
  - Update useTaskValidation hook with cache sync

## Testing
- Direct Track: edit.pdf (3 pages, 1.281s), edit3.pdf (2 pages, 0.203s)
- Cell boxes validation: 43 valid, 0 invalid
- Table merging: 12 merged cells verified

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/hooks/useTaskValidation.ts

@@ -1,6 +1,7 @@
 import { useEffect, useState } from 'react'
 import { useQuery } from '@tanstack/react-query'
 import { useUploadStore } from '@/store/uploadStore'
+import { useTaskStore } from '@/store/taskStore'
 import { apiClientV2 } from '@/services/apiV2'
 import type { TaskDetail } from '@/types/apiV2'
 
@@ -15,13 +16,21 @@ interface UseTaskValidationResult {
 /**
  * Hook for validating task existence and handling deleted tasks gracefully.
  * Shows loading state first, then either returns task data or marks as not found.
+ *
+ * This hook integrates with both uploadStore (legacy) and taskStore (new).
+ * The taskId is sourced from uploadStore.batchId for backward compatibility,
+ * while task metadata is synced to taskStore for caching and state management.
  */
 export function useTaskValidation(options?: {
   refetchInterval?: number | false | ((query: any) => number | false)
 }): UseTaskValidationResult {
+  // Legacy: Get taskId from uploadStore
   const { batchId, clearUpload } = useUploadStore()
   const taskId = batchId ? String(batchId) : null
 
+  // New: Use taskStore for caching and state management
+  const { updateTaskCache, removeFromCache, clearCurrentTask } = useTaskStore()
+
   const [isNotFound, setIsNotFound] = useState(false)
 
   const { data: taskDetail, isLoading, error, isFetching } = useQuery({
@@ -40,16 +49,27 @@ export function useTaskValidation(options?: {
     staleTime: 0,
   })
 
-  // Handle 404 error - mark as not found immediately
+  // Sync task details to taskStore cache when data changes
+  useEffect(() => {
+    if (taskDetail) {
+      updateTaskCache(taskDetail)
+    }
+  }, [taskDetail, updateTaskCache])
+
+  // Handle 404 error - mark as not found and clean up cache
   useEffect(() => {
     if (error && (error as any)?.response?.status === 404) {
       setIsNotFound(true)
+      if (taskId) {
+        removeFromCache(taskId)
+      }
     }
-  }, [error])
+  }, [error, taskId, removeFromCache])
 
   // Clear state and store
   const clearAndReset = () => {
-    clearUpload()
+    clearUpload()       // Legacy store
+    clearCurrentTask()  // New store
     setIsNotFound(false)
   }