fix: follow-up nits for AVIF/JXL brotli support

- Fix JXL container ftyp size check (==20 → >=16) to accept
  wider range of valid JXL files
- Add brotli decompression size limit (2 MB) to prevent OOM
- Add trailing newline to requirements.txt
- Add unit tests for new ISOBMFF/brotli extraction paths:
  JXL/AVIF happy paths, missing brob, corrupt payload,
  non-ISOBMFF fallthrough, write-skip on AVIF/JXL,
  JSON dict/list fields, and oversized decompression

py/utils/exif_utils.py

@@ -43,7 +43,7 @@ class ExifUtils:
             struct.unpack('>I', data[:4])[0] == 12
             and data[4:8] == b'JXL '
             and data[8:12] == bytes([0x0d, 0x0a, 0x87, 0x0a])
-            and struct.unpack('>I', data[12:16])[0] == 20
+            and struct.unpack('>I', data[12:16])[0] >= 16
             and data[16:20] == b'ftyp'
             and data[20:24] == b'jxl '
         )
@@ -57,6 +57,9 @@ class ExifUtils:
                 return True
         return False
 
+    # Max decompressed size for brotli metadata (2 MB)
+    _BROTLI_MAX_DECOMPRESSED = 2 * 1024 * 1024
+
     @staticmethod
     def _extract_isobmff_brotli(image_path: str) -> Optional[dict]:
         try:
@@ -88,6 +91,13 @@ class ExifUtils:
         if _BROTLI_AVAILABLE:
             try:
                 decompressed = brotli.decompress(compressed)
+                if len(decompressed) > ExifUtils._BROTLI_MAX_DECOMPRESSED:
+                    logger.warning(
+                        "Brotli metadata too large (%d bytes, max %d), ignoring",
+                        len(decompressed),
+                        ExifUtils._BROTLI_MAX_DECOMPRESSED,
+                    )
+                    decompressed = None
             except Exception:
                 decompressed = None
         else: