Update paddle, and support invoice line item

AGENTS.md

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+# AGENTS.md - Coding Guidelines for AI Agents
+
+## Build / Test / Lint Commands
+
+### Python Backend
+```bash
+# Install packages (editable mode)
+pip install -e packages/shared
+pip install -e packages/training
+pip install -e packages/backend
+
+# Run all tests
+DB_PASSWORD=xxx pytest tests/ -q
+
+# Run single test file
+DB_PASSWORD=xxx pytest tests/path/to/test_file.py -v
+
+# Run with coverage
+DB_PASSWORD=xxx pytest tests/ --cov=packages --cov-report=term-missing
+
+# Format code
+black packages/ tests/
+ruff check packages/ tests/
+
+# Type checking
+mypy packages/
+```
+
+### Frontend
+```bash
+cd frontend
+
+# Install dependencies
+npm install
+
+# Development server
+npm run dev
+
+# Build
+npm run build
+
+# Run tests
+npm run test
+
+# Run single test
+npx vitest run src/path/to/file.test.ts
+
+# Watch mode
+npm run test:watch
+
+# Coverage
+npm run test:coverage
+```
+
+## Code Style Guidelines
+
+### Python
+
+**Imports:**
+- Use absolute imports within packages: `from shared.pdf.extractor import PDFDocument`
+- Group imports: stdlib → third-party → local (separated by blank lines)
+- Use `from __future__ import annotations` for forward references when needed
+
+**Type Hints:**
+- All functions must have type hints (enforced by mypy)
+- Use `| None` instead of `Optional[...]` (Python 3.10+)
+- Use `list[str]` instead of `List[str]` (Python 3.10+)
+
+**Naming:**
+- Classes: `PascalCase` (e.g., `PDFDocument`, `InferencePipeline`)
+- Functions/variables: `snake_case` (e.g., `extract_text`, `get_db_connection`)
+- Constants: `UPPER_SNAKE_CASE` (e.g., `DEFAULT_DPI`, `DATABASE`)
+- Private: `_leading_underscore` for internal use
+
+**Error Handling:**
+- Use custom exceptions from `shared.exceptions`
+- Base exception: `InvoiceExtractionError`
+- Specific exceptions: `PDFProcessingError`, `OCRError`, `DatabaseError`, etc.
+- Always include context in exceptions via `details` dict
+
+**Docstrings:**
+- Use Google-style docstrings
+- All public functions/classes must have docstrings
+- Include Args/Returns sections for complex functions
+
+**Code Organization:**
+- Maximum line length: 100 characters (black config)
+- Target Python: 3.10+
+- Keep files under 800 lines, ideally 200-400 lines
+
+### TypeScript / React Frontend
+
+**Imports:**
+- Use path alias `@/` for project imports: `import { Button } from '@/components/Button'`
+- Group: React → third-party → local (@/) → relative
+
+**Naming:**
+- Components: `PascalCase` (e.g., `Dashboard.tsx`, `InferenceDemo.tsx`)
+- Hooks: `camelCase` with `use` prefix (e.g., `useDocuments.ts`)
+- Types/Interfaces: `PascalCase` (e.g., `DocumentListResponse`)
+- API endpoints: `camelCase` (e.g., `documentsApi`)
+
+**TypeScript:**
+- Strict mode enabled
+- Use explicit return types on exported functions
+- Prefer `type` over `interface` for simple shapes
+- Use enums for fixed sets of values
+
+**React Patterns:**
+- Functional components with hooks
+- Use React Query for server state
+- Use Zustand for client state (if needed)
+- Props interfaces named `{ComponentName}Props`
+
+**Styling:**
+- Use Tailwind CSS exclusively
+- Custom colors: `warm-*` theme (e.g., `bg-warm-text-secondary`)
+- Component variants defined as objects (see Button.tsx pattern)
+
+**Testing:**
+- Use Vitest + React Testing Library
+- Test files: `{name}.test.ts` or `{name}.test.tsx`
+- Co-locate tests with source files when possible
+
+## Project Structure
+
+```
+packages/
+  shared/       # Shared utilities (PDF, OCR, storage, config)
+  training/     # Training service (GPU, CLI commands)
+  backend/      # Web API + inference (FastAPI)
+frontend/       # React + TypeScript + Vite
+tests/          # Test suite
+migrations/     # Database SQL migrations
+```
+
+## Key Configuration
+
+- **DPI:** 150 (must match between training and inference)
+- **Database:** PostgreSQL (configured via env vars)
+- **Storage:** Abstracted (Local/Azure/S3 via storage.yaml)
+- **Python:** 3.10+ (3.11 recommended, 3.10 for RTX 50 series)
+
+## Environment Variables
+
+Required: `DB_PASSWORD`
+Optional: `DB_HOST`, `DB_PORT`, `DB_NAME`, `DB_USER`, `STORAGE_BASE_PATH`
+
+## Common Patterns
+
+### Python: Adding a New API Endpoint
+1. Add route in `backend/web/api/v1/`
+2. Define Pydantic schema in `backend/web/schemas/`
+3. Implement service logic in `backend/web/services/`
+4. Add tests in `tests/web/`
+
+### Frontend: Adding a New Component
+1. Create component in `frontend/src/components/`
+2. Export from `frontend/src/components/index.ts` if shared
+3. Add types to `frontend/src/api/types.ts` if API-related
+4. Add tests co-located with component
+
+### Error Handling
+```python
+from shared.exceptions import DatabaseError
+
+try:
+    result = db.query(...)
+except Exception as e:
+    raise DatabaseError(f"Failed to fetch document: {e}", details={"doc_id": doc_id})
+```
+
+### Database Access
+```python
+from shared.data.repositories import DocumentRepository
+
+repo = DocumentRepository()
+doc = repo.get_by_id(doc_id)
+```