refactor: complete V1 to V2 migration and remove legacy architecture

Remove all V1 architecture components and promote V2 to primary:
- Delete all paddle_ocr_* table models (export, ocr, translation, user)
- Delete legacy routers (auth, export, ocr, translation)
- Delete legacy schemas and services
- Promote user_v2.py to user.py as primary user model
- Update all imports and dependencies to use V2 models only
- Update main.py version to 2.0.0

Database changes:
- Fix SQLAlchemy reserved word: rename audit_log.metadata to extra_data
- Add migration to drop all paddle_ocr_* tables
- Update alembic env to only import V2 models

Frontend fixes:
- Fix Select component exports in TaskHistoryPage.tsx
- Update to use simplified Select API with options prop
- Fix AxiosInstance TypeScript import syntax

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

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

backend/app/main.py

@@ -1,5 +1,5 @@
 """
-Tool_OCR - FastAPI Application Entry Point
+Tool_OCR - FastAPI Application Entry Point (V2)
 Main application setup with CORS, routes, and startup/shutdown events
 """
 
@@ -7,11 +7,9 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from contextlib import asynccontextmanager
 import logging
-import asyncio
 from pathlib import Path
 
 from app.core.config import settings
-from app.services.background_tasks import task_manager
 
 # Ensure log directory exists before configuring logging
 Path(settings.log_file).parent.mkdir(parents=True, exist_ok=True)
@@ -32,19 +30,12 @@ logger = logging.getLogger(__name__)
 async def lifespan(app: FastAPI):
     """Application lifespan events"""
     # Startup
-    logger.info("Starting Tool_OCR application...")
+    logger.info("Starting Tool_OCR V2 application...")
 
     # Ensure all directories exist
     settings.ensure_directories()
     logger.info("All directories created/verified")
 
-    # Start cleanup scheduler as background task
-    cleanup_task = asyncio.create_task(task_manager.start_cleanup_scheduler())
-    logger.info("Started cleanup scheduler for expired files")
-
-    # TODO: Initialize database connection pool
-    # TODO: Load PaddleOCR models
-
     logger.info("Application startup complete")
 
     yield
@@ -52,21 +43,12 @@ async def lifespan(app: FastAPI):
     # Shutdown
     logger.info("Shutting down Tool_OCR application...")
 
-    # Cancel cleanup task
-    cleanup_task.cancel()
-    try:
-        await cleanup_task
-    except asyncio.CancelledError:
-        logger.info("Cleanup scheduler stopped")
-
-    # TODO: Close database connections
-
 
 # Create FastAPI application
 app = FastAPI(
-    title="Tool_OCR",
-    description="OCR Batch Processing System with Structure Extraction",
-    version="0.1.0",
+    title="Tool_OCR V2",
+    description="OCR Processing System with External Authentication & Task Isolation",
+    version="2.0.0",
     lifespan=lifespan,
 )
 
@@ -88,8 +70,8 @@ async def health_check():
 
     response = {
         "status": "healthy",
-        "service": "Tool_OCR",
-        "version": "0.1.0",
+        "service": "Tool_OCR V2",
+        "version": "2.0.0",
     }
 
     # Add GPU status information
@@ -134,26 +116,17 @@ async def health_check():
 async def root():
     """Root endpoint with API information"""
     return {
-        "message": "Tool_OCR API",
-        "version": "0.1.0",
+        "message": "Tool_OCR API V2 - External Authentication",
+        "version": "2.0.0",
         "docs_url": "/docs",
         "health_check": "/health",
     }
 
 
-# Include API routers
-from app.routers import auth, ocr, export, translation
-# V2 routers with external authentication
-from app.routers import auth_v2, tasks, admin
+# Include V2 API routers
+from app.routers import auth, tasks, admin
 
-# Legacy V1 routers
 app.include_router(auth.router)
-app.include_router(ocr.router)
-app.include_router(export.router)
-app.include_router(translation.router)  # RESERVED for Phase 5
-
-# New V2 routers with external authentication
-app.include_router(auth_v2.router)
 app.include_router(tasks.router)
 app.include_router(admin.router)