0.1.0-dev.1

Major refactoring: Split large files into modular packages

## Python Modules
- Split docling_chunker.py into server/python/docling/ package
  - progress_tracker.py, pdf_utils.py, resume_manager.py
  - output_writer.py, converter_config.py, main.py
- Split image_processor.py into server/python/vision/ package
  - backends.py, extractors.py, smolvlm.py, gemini.py
  - description_injector.py, processor.py

## JavaScript/React Modules
- Split ChatInterface.jsx into hooks and components
  - useChatThreads, useChatMessages, useVectorDb, useServerStatus, useModelSelector
  - ChatMessage, ChatInputArea, ChatWelcome, StatusIndicators
- Split ai.service.js into provider pattern
  - BaseProvider, OpenAIProvider, AnthropicProvider, MoonshotProvider, GeminiProvider
  - stream-parser, rate-limiter utilities
- Split embedding.service.js into separate concerns
  - hardware-detector, python-bridge, job-manager, hnsw-manager, models
- Split RAGTestingStep.jsx into modular components
  - useVectorDbs, useSearch hooks
  - VectorDbList, SearchParams, SearchResults, DeleteConfirmModal

## New Features
- Centralized error handling middleware with custom error classes
- API validation with Zod schemas
- Environment configuration with .env.example
- Security documentation (docs/SECURITY.md)
- Unit test structure with Vitest

## Dependencies
- Added zod for schema validation
- Added vitest, jest, @testing-library for testing

All original files maintain backward compatibility via re-exports.