feat: add table detection options and scan artifact removal

- Add TableDetectionSelector component for wired/wireless/region detection
- Add CV-based table line detector module (disabled due to poor performance)
- Add scan artifact removal preprocessing step (removes faint horizontal lines)
- Add PreprocessingConfig schema with remove_scan_artifacts option
- Update frontend PreprocessingSettings with scan artifact toggle
- Integrate table detection config into ProcessingPage
- Archive extract-table-cell-boxes proposal

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

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

frontend/src/pages/ProcessingPage.tsx

@@ -12,9 +12,10 @@ import { Play, CheckCircle, FileText, AlertCircle, Clock, Activity, Loader2, Inf
 import LayoutModelSelector from '@/components/LayoutModelSelector'
 import PreprocessingSettings from '@/components/PreprocessingSettings'
 import PreprocessingPreview from '@/components/PreprocessingPreview'
+import TableDetectionSelector from '@/components/TableDetectionSelector'
 import TaskNotFound from '@/components/TaskNotFound'
 import { useTaskValidation } from '@/hooks/useTaskValidation'
-import type { LayoutModel, ProcessingOptions, PreprocessingMode, PreprocessingConfig, DocumentAnalysisResponse } from '@/types/apiV2'
+import type { LayoutModel, ProcessingOptions, PreprocessingMode, PreprocessingConfig, TableDetectionConfig, DocumentAnalysisResponse } from '@/types/apiV2'
 
 export default function ProcessingPage() {
   const { t } = useTranslation()
@@ -44,9 +45,17 @@ export default function ProcessingPage() {
     sharpen: true,
     sharpen_strength: 1.0,
     binarize: false,
+    remove_scan_artifacts: true,
   })
   const [showPreview, setShowPreview] = useState(false)
 
+  // Table detection state
+  const [tableDetectionConfig, setTableDetectionConfig] = useState<TableDetectionConfig>({
+    enable_wired_table: true,
+    enable_wireless_table: true,
+    enable_region_detection: true,
+  })
+
   // Analyze document to determine if OCR is needed (only for pending tasks)
   const { data: documentAnalysis, isLoading: isAnalyzing } = useQuery({
     queryKey: ['documentAnalysis', taskId],
@@ -70,6 +79,7 @@ export default function ProcessingPage() {
         layout_model: layoutModel,
         preprocessing_mode: preprocessingMode,
         preprocessing_config: preprocessingMode === 'manual' ? preprocessingConfig : undefined,
+        table_detection: tableDetectionConfig,
       }
 
       return apiClientV2.startTask(taskId!, options)
@@ -441,6 +451,13 @@ export default function ProcessingPage() {
                 disabled={processOCRMutation.isPending}
               />
 
+              {/* Table Detection Settings */}
+              <TableDetectionSelector
+                value={tableDetectionConfig}
+                onChange={setTableDetectionConfig}
+                disabled={processOCRMutation.isPending}
+              />
+
               {/* Preprocessing Settings */}
               <PreprocessingSettings
                 mode={preprocessingMode}