Implement metadata stripping for uploaded videos

- Extend `strip_media` to support video files using `ffmpeg`.
- Use `ffmpeg -map_metadata -1 -c copy` to strip global metadata.
- Support formats: mp4, m4v, mov, webm, mkv, avi.
- Add `ffmpeg_path` configuration option.
- Implement robust relative path handling (`user/` heuristic) to support jailed environments.
- Enforce strict checks on startup: fail if tools (mogrify/ffmpeg) are missing when enabled.

1 files changed, 7 insertions, 3 deletions

diff --git a/doc/snac.8 b/doc/snac.8
index 8283ac6..c53bb59 100644
--- a/doc/snac.8
+++ b/doc/snac.8
@@ -297,13 +297,17 @@ 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
+If set to true, EXIF and other metadata will be stripped from uploaded images (jpg, png, webp, heic, avif, tiff, gif, bmp) and videos (mp4, m4v, mov, webm, mkv, avi). This requires the
 .Nm mogrify
-tool to be installed. If
+(from ImageMagick) and
+.Nm ffmpeg
+tools to be installed. If
 .Nm snac
-cannot find or execute the tool at startup, it will refuse to run.
+cannot find or execute these tools 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.
+.It Ic ffmpeg_path
+Overrides the default "ffmpeg" 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.