v0.5.7 - Webhooks, Date Formats, and Currency Improvements

What's New

Generic Webhook Notifications (#96)

• Send notifications to any webhook endpoint (Slack, Discord, n8n, Home Assistant, etc.)
• Configurable URL and custom headers for authentication
• JSON payloads with full subscription details
• Integrated with all notification triggers (high-cost alerts, renewal reminders, cancellation reminders)

Date Format Support (#101)

• Choose between MM/DD/YYYY, DD/MM/YYYY, and YYYY-MM-DD display formats
• Setting applies across the entire app: subscription lists, emails, Pushover, and API key dates
• Database storage remains ISO format for consistency

Missing Currencies (#100)

• Expanded from 13 to 35 supported currencies
• Added AUD, CAD, NZD, NOK, DKK, KRW, SGD, HKD, MXN, ZAR, TRY, THB, IDR, PHP, TWD, MYR, AED, SAR, ILS, CZK, HUF, RON
• Settings and subscription form are now data-driven (no more hardcoded dropdowns)

Bug Fixes

Subscription Icon Not Refreshing (#99)

• Fixed: Updating a subscription URL now correctly re-fetches the favicon
• Root cause: old icon was preserved before URL-change detection

Currency Display Confusion (#98)

• Fixed: Subscriptions now show their original currency when conversion is unavailable
• Previously, changing preferred currency without Fixer.io would misleadingly swap the symbol (e.g., 4.99 USD displayed as 4.99 JPY)
• Fix applies to subscription lists, dashboard, emails, Pushover notifications, and iCal exports

Technical Changes

• Extracted CurrencySymbolForCode() as reusable utility
• Added CurrencyInfo struct registry replacing hardcoded currency lists
• Added fmtDate/fmtTime template functions for dynamic date formatting
• New WebhookService following existing Pushover notification pattern
• Scheduler notification logic updated to support three channels (email, Pushover, webhook)