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/schemas/__init__.py

@@ -1,59 +1,30 @@
 """
-Tool_OCR - API Schemas
+Tool_OCR - API Schemas (V2)
 Pydantic models for request/response validation
 """
 
-from app.schemas.auth import Token, TokenData, LoginRequest
-from app.schemas.user import UserBase, UserCreate, UserResponse
-from app.schemas.ocr import (
-    OCRBatchResponse,
-    OCRFileResponse,
-    OCRResultResponse,
-    BatchStatusResponse,
-    FileStatusResponse,
-    ProcessRequest,
-    ProcessResponse,
-)
-from app.schemas.export import (
-    ExportRequest,
-    ExportRuleCreate,
-    ExportRuleUpdate,
-    ExportRuleResponse,
-    CSSTemplateResponse,
-)
-from app.schemas.translation import (
-    TranslationRequest,
-    TranslationResponse,
-    TranslationFeatureStatus,
-    LanguageInfo,
+from app.schemas.auth import LoginRequest, Token, UserResponse
+from app.schemas.task import (
+    TaskCreate,
+    TaskUpdate,
+    TaskResponse,
+    TaskDetailResponse,
+    TaskListResponse,
+    TaskStatsResponse,
+    TaskStatusEnum,
 )
 
 __all__ = [
     # Auth
-    "Token",
-    "TokenData",
     "LoginRequest",
-    # User
-    "UserBase",
-    "UserCreate",
+    "Token",
     "UserResponse",
-    # OCR
-    "OCRBatchResponse",
-    "OCRFileResponse",
-    "OCRResultResponse",
-    "BatchStatusResponse",
-    "FileStatusResponse",
-    "ProcessRequest",
-    "ProcessResponse",
-    # Export
-    "ExportRequest",
-    "ExportRuleCreate",
-    "ExportRuleUpdate",
-    "ExportRuleResponse",
-    "CSSTemplateResponse",
-    # Translation (RESERVED)
-    "TranslationRequest",
-    "TranslationResponse",
-    "TranslationFeatureStatus",
-    "LanguageInfo",
+    # Task
+    "TaskCreate",
+    "TaskUpdate",
+    "TaskResponse",
+    "TaskDetailResponse",
+    "TaskListResponse",
+    "TaskStatsResponse",
+    "TaskStatusEnum",
 ]