Release v0.2.0: simplified startup, parallel dependency resolution

What's new in v0.2.0:

• Removed runner/context setup from users
• Added internal graceful shutdown logic via signal handling
• Dependencies now resolved in parallel for faster startup
• RunAllComponents returns shutdown wait func
• Refactored tests, removed errgroup from public API
• Simplified examples

This version is backward-incompatible due to changes in RunAllComponents.