feat: enable document orientation detection for scanned PDFs

- Enable PP-StructureV3's use_doc_orientation_classify feature
- Detect rotation angle from doc_preprocessor_res.angle
- Swap page dimensions (width <-> height) for 90°/270° rotations
- Output PDF now correctly displays landscape-scanned content

Also includes:
- Archive completed openspec proposals
- Add simplify-frontend-ocr-config proposal (pending)
- Code cleanup and frontend simplification

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/store/taskStore.ts

@@ -140,12 +140,16 @@ export const useTaskStore = create<TaskState>()(
       updateTaskCache: (task) => {
         set((state) => {
           const taskId = 'task_id' in task ? task.task_id : task.taskId
+          // Extract processing track from either Task (snake_case) or CachedTask (camelCase)
+          const track = 'processing_track' in task
+            ? task.processing_track
+            : ('processingTrack' in task ? task.processingTrack : undefined)
           const cached: CachedTask = {
             taskId,
             filename: task.filename || null,
             status: task.status,
             updatedAt: new Date().toISOString(),
-            processingTrack: 'processing_track' in task ? task.processing_track : task.processingTrack,
+            processingTrack: track,
           }
 
           // Remove existing entry if present