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/db/queries.go

@@ -798,6 +798,49 @@ func (s *Store) InsertPricePoint(ctx context.Context, p *models.PricePoint) erro
 	return err
 }
 
+// LoadRecentPriceHistory bulk-loads the last `perItem` price points (oldest →
+// newest) for each item id. Returns a map keyed by item id; items with no
+// history are absent from the map. Used by the items list page to render a
+// sparkline per row without N+1 queries.
+func (s *Store) LoadRecentPriceHistory(ctx context.Context, ids []int64, perItem int) (map[int64][]models.PricePoint, error) {
+	out := make(map[int64][]models.PricePoint, len(ids))
+	if len(ids) == 0 || perItem <= 0 {
+		return out, nil
+	}
+	placeholders := make([]string, len(ids))
+	args := make([]any, 0, len(ids)+1)
+	for i, id := range ids {
+		placeholders[i] = "?"
+		args = append(args, id)
+	}
+	args = append(args, perItem)
+	q := `
+		WITH ranked AS (
+			SELECT item_id, price, store, polled_at,
+			       ROW_NUMBER() OVER (PARTITION BY item_id ORDER BY polled_at DESC) AS rn
+			FROM price_history
+			WHERE item_id IN (` + strings.Join(placeholders, ",") + `)
+		)
+		SELECT item_id, price, store, polled_at FROM ranked WHERE rn <= ?
+		ORDER BY item_id, polled_at ASC
+	`
+	rows, err := s.DB.QueryContext(ctx, q, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var p models.PricePoint
+		var store sql.NullString
+		if err := rows.Scan(&p.ItemID, &p.Price, &store, &p.PolledAt); err != nil {
+			return nil, err
+		}
+		p.Store = s.dec(store.String)
+		out[p.ItemID] = append(out[p.ItemID], p)
+	}
+	return out, rows.Err()
+}
+
 func (s *Store) ListPriceHistory(ctx context.Context, itemID int64) ([]models.PricePoint, error) {
 	rows, err := s.DB.QueryContext(ctx,
 		`SELECT id, item_id, price, store, polled_at FROM price_history WHERE item_id = ? ORDER BY polled_at ASC`,