Add bambu-nfc dump parse, Key-A HKDF, and spool merge.

Parse filanfc-dump/v1 zip/JSON, Bambu 1K images, and merge stickers by tray UID. dump and mifare packages stay importable for a later common library.

mifare/mifare.go

@@ -0,0 +1,36 @@
+// Package mifare holds MIFARE Classic 1K layout helpers with no brand-specific memory map.
+package mifare
+
+import "fmt"
+
+const (
+	Sectors    = 16
+	Blocks     = 64
+	BlockSize  = 16
+	SectorSize = 64
+	Size1K     = 1024
+)
+
+// SectorOf returns the sector index for a block number (0–63).
+func SectorOf(block int) int {
+	return block / 4
+}
+
+// BlockRange returns the half-open block range [first, last) for a sector.
+func BlockRange(sector int) (first, last int) {
+	first = sector * 4
+	last = first + 4
+	return first, last
+}
+
+// SectorBytes returns the 64-byte slice for sector (0–15) from a 1K image.
+func SectorBytes(image []byte, sector int) ([]byte, error) {
+	if len(image) != Size1K {
+		return nil, fmt.Errorf("image size: want %d got %d", Size1K, len(image))
+	}
+	if sector < 0 || sector >= Sectors {
+		return nil, fmt.Errorf("sector %d out of range", sector)
+	}
+	off := sector * SectorSize
+	return image[off : off+SectorSize], nil
+}