Implement configurable EXIF stripping for uploaded media

- Add `strip_exif` configuration option to enable metadata removal.
- Add `mogrify_path` configuration to specify external tool location.
- Implement strip_media using `mogrify -strip`.
- Support multiple image formats: jpg, png, webp, heic, heif, avif, tiff, gif, bmp.
- Add strict startup check: fail to start if `strip_exif` is enabled but `mogrify` is missing/broken.
- Update documentation in `doc/snac.8`.

1 files changed, 8 insertions, 0 deletions

diff --git a/doc/snac.8 b/doc/snac.8
index b8a75fa..8283ac6 100644
--- a/doc/snac.8
+++ b/doc/snac.8
@@ -296,6 +296,14 @@ outgoing messages (default: 15). Anyway, whenever any incoming activity from a
 failed instance is detected, this counter is reset for it.
 .It Ic vkey
 Public vapid key. Used for notification on some client.
+.It Ic strip_exif
+If set to true, EXIF metadata will be stripped from uploaded images (jpg, png, webp, heic, avif, tiff, gif, bmp). This requires the
+.Nm mogrify
+tool to be installed. If
+.Nm snac
+cannot find or execute the tool at startup, it will refuse to run.
+.It Ic mogrify_path
+Overrides the default "mogrify" command name or path. Use this if the tool is not in the system PATH or has a different name.
 .El
 .Pp
 You must restart the server to make effective these changes.