imagenorm decoded and re-encoded to JPEG but ignored the EXIF Orientation
tag. Phone cameras store the sensor pixels one way and set an EXIF flag to
rotate on display, so a "portrait" JPEG is really a landscape bitmap tagged
"rotate 90°" — and our re-encode strips EXIF, so without baking the rotation
in, a packet photographed in portrait reaches the vision model sideways
(bad OCR) and any future thumbnail is wrong.

- exifOrientation: a small pure-Go parser that walks the JPEG APP1/Exif
  segment for tag 0x0112, returning 1 (normal) for non-JPEG or unparseable
  input — never guess a rotation onto a correct image. No cgo, no new dep.
- applyOrientation: bakes in all 8 orientations (the 4 rotations + mirrors)
  after downscale (cheaper to rotate the small image; a 90° turn swaps the
  sides but not the longest edge, so the downscale bound still holds).
- Non-JPEG paths (HEIC/webp/png) are untouched — their decoders own
  orientation and they carry no JPEG EXIF.

Tests build oriented JPEGs (a corner marker + a spliced Exif APP1) and
assert the marker lands where each orientation says, dims swapping for the
quarter-turns; plus parser defaults for non-JPEG / no-EXIF / garbage.
Stays CGO_ENABLED=0.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

@@ -191,0 +211,4 @@
+	b := img.Bounds()
+	w, h := b.Dx(), b.Dy()
+	swap := o >= 5 // a quarter-turn: output dimensions transpose
+	dst := image.NewRGBA(image.Rect(0, 0, w, h))

@@ -191,0 +215,4 @@
+	if swap {
+		dst = image.NewRGBA(image.Rect(0, 0, h, w))
+	}
+	for y := range h {

@@ -191,0 +246,4 @@
+// a wrong guess rotates a correct image. Only the JPEG APP1/Exif path is parsed:
+// that's the format uploaded phone photos overwhelmingly arrive in, and the other
+// decoders own their own orientation.
+func exifOrientation(raw []byte) int {

@@ -191,0 +253,4 @@
+		return 1
+	}
+	for i := 2; i+4 <= len(raw); {
+		if raw[i] != 0xFF {

@@ -191,0 +277,4 @@
+// orientationFromApp1 reads the Orientation tag from a JPEG APP1 segment body
+// (everything after the 2-byte length): "Exif\0\0" then a TIFF block holding
+// IFD0. Returns (0, false) if the segment isn't Exif or the tag is missing.
+func orientationFromApp1(seg []byte) (int, bool) {

@@ -191,0 +302,4 @@
+		if off+12 > len(tiff) {
+			return 0, false
+		}
+		if bo.Uint16(tiff[off:off+2]) != 0x0112 { // Orientation tag

@@ -203,0 +268,4 @@
+	// The white marker starts centred at (10,6) in the 40x24 source. For each
+	// orientation, wantW/H is the corrected canvas and (mx,my) is where that
+	// marker must land — derived from the same transform Normalize applies.
+	cases := []struct {

@@ -203,0 +273,4 @@
+		wantW, wantH int
+		mx, my       int
+	}{
+		{0, 40, 24, 10, 6},  // no EXIF → unchanged, marker top-left

@@ -203,0 +279,4 @@
+		{6, 24, 40, 17, 10}, // 90° CW → top-right (dims swap)
+		{8, 24, 40, 6, 29},  // 90° CCW → bottom-left (dims swap)
+	}
+	for _, tc := range cases {