When a product no longer appears in a successful scrape for its
retailer+caliber, mark it out of stock. After each scrape cycle, hard
delete any product whose last_seen_at is older than 30 days (snapshots
cascade via FK). A zero-result scrape leaves existing listings alone so
a parse failure or transient site glitch can't nuke the catalog.
Add True Shot Ammo (Shopify JSON), Palmetto State Armory (Magento HTML),
Bulk Ammo (Magento HTML), and Natchez Shooters Supply (GraphQL API).
Extends scraper infrastructure with HttpClient.post_json/3 and an
optional fetch/2 callback on the Scraper behaviour for scrapers that
need custom HTTP flows (e.g. GraphQL POST requests).
- 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¢)
