Previously combined as a single "556-223" caliber. Now tracked separately
with dedicated scraper URLs per retailer. Also fixes broken URLs for
Lucky Gunner, True Shot Ammo, and Palmetto State Armory.
- Add subsonic boolean field to products with composite filter indexes
- Add TextDetector utility for detecting subsonic/casing from product titles
- Wire TextDetector into SgAmmo (casing + subsonic) and LuckyGunner (subsonic + fallback casing)
- Extend latest_prices_for_caliber with casing, grain_weight, and subsonic filter options
- Add distinct_grain_weights_for_caliber and distinct_casings_for_caliber queries
- Add filter UI with toggleable casing, grain weight, and subsonic buttons
- Add grain weight column and subsonic badge to product table
- Refresh filter options on PubSub price updates for real-time UI
- Implement Target Sports USA scraper with 18 caliber mappings
- Display all prices in dollar format ($0.38 instead of 38¢)
