Add version tracking and v1.0.0 release

- Create CHANGELOG.md documenting all features
- Add version.json for version tracking
- Display version in Settings page footer with links to Changelog and GitHub
- Tag release as v1.0.0

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

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+# Changelog
+
+All notable changes to PriceGhost will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.0.0] - 2026-01-23
+
+### Added
+
+#### Core Features
+- Universal price scraping with site-specific extractors for Amazon, Walmart, Best Buy, Target, eBay, Newegg, Home Depot, Costco, and AliExpress
+- JSON-LD structured data extraction for broad site compatibility
+- Puppeteer headless browser fallback with stealth plugin for JavaScript-rendered pages
+- Price history tracking with interactive charts (7d, 30d, 90d, all time)
+- 7-day sparkline graphs on dashboard for quick trend overview
+- Configurable check intervals (5 minutes to 24 hours)
+- Live countdown timers and progress bars showing time until next check
+- Staggered checking with jitter to prevent rate limiting
+
+#### AI Features
+- AI-powered price extraction fallback (Anthropic Claude, OpenAI GPT, Ollama local)
+- AI price verification to catch scraping errors (e.g., scraping savings amounts instead of actual prices)
+- AI status badges showing verification status (✓ verified, ⚡ corrected)
+
+#### Notifications
+- Telegram bot notifications
+- Discord webhook notifications
+- Pushover push notifications
+- ntfy.sh notifications (no account required)
+- Price drop alerts with configurable thresholds
+- Target price alerts
+- Back-in-stock alerts
+- Per-channel enable/disable toggles
+- Test notification buttons for each channel
+
+#### Stock Tracking
+- Out-of-stock detection with visual indicators
+- Stock status history tracking
+- Stock timeline visualization
+- Back-in-stock notification alerts
+
+#### User Interface
+- Dark/Light mode with system theme auto-detection
+- Responsive design for desktop and mobile
+- Toast notifications for user feedback
+- Dashboard with list layout, search, and sorting
+- Bulk actions (select multiple products, bulk delete)
+- Historical low price indicators
+- Product notification badges showing configured alerts
+
+#### User Management
+- Multi-user support with JWT authentication
+- Admin panel for user management
+- Registration enable/disable control
+- Profile management (name, password)
+- Password visibility toggle for sensitive fields
+
+#### PWA & Mobile
+- Progressive Web App support
+- Add to Home Screen capability
+- Service worker for offline caching
+- Custom ghost icon
+
+#### Currency Support
+- USD, EUR, GBP, CHF, CAD, AUD, JPY, INR support
+- Automatic currency detection from scraped pages
+
+#### Deployment
+- Docker and Docker Compose support
+- GitHub Container Registry images
+- GitHub Actions CI/CD workflow
+
+### Security
+- JWT-based authentication
+- bcrypt password hashing
+- Input validation throughout
+- Secure API design
+
+---
+
+## Version History
+
+| Version | Date | Description |
+|---------|------|-------------|
+| 1.0.0 | 2026-01-23 | Initial public release |