feat: Add complete monetization system

Backend:
- User authentication with JWT tokens (auth_service.py)
- Subscription plans: Free, Starter (), Pro (), Business (), Enterprise
- Stripe integration for payments (payment_service.py)
- Usage tracking and quotas
- Credit packages for pay-per-use
- Plan-based provider restrictions

Frontend:
- Landing page with hero, features, pricing preview (landing-sections.tsx)
- Pricing page with all plans and credit packages (/pricing)
- User dashboard with usage stats (/dashboard)
- Login/Register pages with validation (/auth/login, /auth/register)
- Ollama self-hosting setup guide (/ollama-setup)
- Updated sidebar with user section and plan badge

Monetization strategy:
- Freemium: 3 docs/day, Ollama only
- Starter: 50 docs/month, Google Translate
- Pro: 200 docs/month, all providers, API access
- Business: 1000 docs/month, team management
- Enterprise: Custom pricing, SLA

Self-hosted option:
- Free unlimited usage with own Ollama server
- Complete privacy (data never leaves machine)
- Step-by-step setup guide included

main.py

@@ -22,6 +22,9 @@ from config import config
 from translators import excel_translator, word_translator, pptx_translator
 from utils import file_handler, handle_translation_error, DocumentProcessingError
 
+# Import auth routes
+from routes.auth_routes import router as auth_router
+
 # Import SaaS middleware
 from middleware.rate_limiting import RateLimitMiddleware, RateLimitManager, RateLimitConfig
 from middleware.security import SecurityHeadersMiddleware, RequestLoggingMiddleware, ErrorHandlingMiddleware
@@ -174,6 +177,9 @@ static_dir = Path(__file__).parent / "static"
 if static_dir.exists():
     app.mount("/static", StaticFiles(directory=str(static_dir)), name="static")
 
+# Include auth routes
+app.include_router(auth_router)
+
 
 # Custom exception handler for ValidationError
 @app.exception_handler(ValidationError)