feat: implement complete Universal Language Connector system

Implement comprehensive LSP-based universal plugin architecture for
multi-editor document conversion.

Server Implementation:
- Complete Rust server with LSP 3.17, HTTP REST API, and WebSocket support
- Document conversion engine (Markdown ↔ HTML ↔ JSON)
- Concurrent document storage using dashmap (lock-free)
- Performance targets: <100ms response, <50MB memory, <500ms startup

Client Implementations (all <100 LOC):
- VS Code extension (~70 LOC)
- Neovim plugin (~65 LOC)
- Emacs package (~75 LOC)
- JetBrains plugin (~55 LOC)
- Sublime Text plugin (~60 LOC)
- Zed and Helix configurations

Web UI:
- Single-page application with real-time dashboard
- Live document converter
- WebSocket integration for real-time updates
- Document manager interface

Infrastructure:
- Dockerfile and container orchestration (docker-compose, podman-compose)
- Comprehensive Makefile build system
- Complete test suites (LSP compliance, HTTP API, core engine)

Documentation:
- Complete API documentation
- CONTRIBUTING.md with development guidelines
- README.md with quick start and architecture overview
- Example configurations and conversion samples

Architecture Principles:
- All logic in server, clients are thin wrappers
- LSP 3.17 strict compliance
- Server-first thinking for consistency
- "Write once, run everywhere" via LSP

Author: claude

.gitignore

@@ -0,0 +1,60 @@
+# Rust
+target/
+Cargo.lock
+**/*.rs.bk
+*.pdb
+
+# Node.js / VS Code client
+node_modules/
+dist/
+out/
+*.vsix
+package-lock.json
+
+# Python / Sublime
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+
+# IDEs
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# Build artifacts
+*.exe
+*.dll
+*.dylib
+
+# Logs
+*.log
+logs/
+
+# Environment
+.env
+.env.local
+*.local
+
+# Coverage
+coverage/
+*.profdata
+tarpaulin-report.html
+
+# Benchmarks
+criterion/
+
+# Temporary files
+*.tmp
+*.temp
+.cache/
+
+# Docker
+.dockerignore
+
+# OS
+Thumbs.db