Initial commit: Add Pstryk Energy Card v4.1.0

- Add main card implementation with full/compact/super_compact modes
- Support for sparkline and bars widgets with effects
- Price color coding based on best/worst price ranges
- Alert system for high/low price thresholds
- Polish/English translations support
- HACS integration configuration
- Development guidelines in AGENTS.md

AGENTS.md

@@ -0,0 +1,27 @@
+# Agent Guidelines for Pstryk Energy Card
+
+## Build/Test Commands
+- No build system - single JavaScript file (`pstryk-card.js`)
+- Test by adding card to Home Assistant dashboard
+- Debug mode: set `debug: true` in card config
+- No linting/formatting tools configured
+
+## Code Style Guidelines
+- **Language**: Vanilla JavaScript ES6+ (no frameworks)
+- **File structure**: Single file with embedded CSS in template literals
+- **Class naming**: PascalCase (e.g., `PstrykCard`)
+- **Method naming**: camelCase with underscore prefix for private methods (e.g., `_getTranslations`)
+- **Variables**: camelCase, use const/let appropriately
+- **Comments**: Polish comments for user-facing text, English for technical notes
+- **Error handling**: Throw descriptive Error objects in `setConfig()` for validation
+- **Translations**: Support PL/EN via `_getTranslations()` method
+- **CSS**: Use CSS custom properties for theming, embed in `<style>` tags
+- **SVG**: Inline SVG for charts, use viewBox for responsiveness
+- **Home Assistant**: Follow custom card conventions, register with `customElements.define()`
+
+## Key Patterns
+- Shadow DOM for encapsulation
+- Lifecycle methods: `connectedCallback()`, `disconnectedCallback()`
+- Config validation in `setConfig()`
+- Performance optimization in `set hass()` with change detection
+- Timer management for hourly refreshes