Items-list sparklines, retro CSS, pinned tooling, deploy docs

- Bulk-load recent price points per item and render a sparkline in
  the items list (new LoadRecentPriceHistory query avoids N+1).
- Add retro.css visual layer and refreshed login/items/layout styling.
- Swap the logo from webp to avif.
- Pin htmx/Chart.js/Tailwind/templ versions in the Makefile with
  vendor / tools / update-deps targets; README documents the
  dependency-bump flow and the hardened systemd deploy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/handlers/items.go

@@ -30,11 +30,22 @@ func (a *App) GetItems(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 	cats, _ := a.Store.ListCategories(r.Context())
+
+	// Bulk-load recent price history so each row can render a sparkline
+	// without N+1 queries. 20 points is enough for a meaningful trend line
+	// at 80px wide and stays cheap on the largest realistic watchlists.
+	ids := make([]int64, 0, len(items))
+	for _, it := range items {
+		ids = append(ids, it.ID)
+	}
+	history, _ := a.Store.LoadRecentPriceHistory(r.Context(), ids, 20)
+
 	render(w, r, templates.Items(templates.ItemsData{
 		Page:             a.page(r, "Items", "items"),
 		Items:            items,
 		Categories:       cats,
 		SelectedCategory: cat,
+		PriceHistory:     history,
 	}))
 }
 
@@ -387,7 +398,8 @@ func (a *App) PostToggleItem(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	a.Scheduler.SyncItem(*it)
-	render(w, r, templates.ItemRow(*it, a.Auth.CSRFToken(r.Context())))
+	hist, _ := a.Store.LoadRecentPriceHistory(r.Context(), []int64{id}, 20)
+	render(w, r, templates.ItemRow(*it, a.Auth.CSRFToken(r.Context()), hist[id]))
 }
 
 func (a *App) PostDeleteItem(w http.ResponseWriter, r *http.Request) {