feat(attachment): reject attachments larger than 1 GiB

Relay's default `max_upload_size` is 1 GiB — any attachment above that
can't be delivered, TUS or inline. Check the size when the attachment
is registered and drop oversized ones with a warn log naming the file
and the cap.

Also add an info log when a large (>= 100 MiB) attachment is attached,
so users see that it'll be routed through TUS, and fix the stale
`100 MB` unit comment on `SENTRY_LARGE_ATTACHMENT_SIZE` — the value is
100 MiB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jpnurmi

src/sentry_attachment.c

@@ -1,5 +1,6 @@
 #include "sentry_attachment.h"
 #include "sentry_alloc.h"
+#include "sentry_logger.h"
 #include "sentry_path.h"
 #include "sentry_string.h"
 
@@ -158,6 +159,18 @@ sentry__attachments_add(sentry_attachment_t **attachments_ptr,
     if (!attachment) {
         return NULL;
     }
+    size_t size = sentry__attachment_get_size(attachment);
+    if (size > SENTRY_MAX_ATTACHMENT_SIZE) {
+        SENTRY_WARNF("rejected oversized attachment \"%s\" (%zu > %d MiB)",
+            sentry__attachment_get_filename(attachment), size / (1024 * 1024),
+            SENTRY_MAX_ATTACHMENT_SIZE / (1024 * 1024));
+        sentry__attachment_free(attachment);
+        return NULL;
+    }
+    if (size >= SENTRY_LARGE_ATTACHMENT_SIZE) {
+        SENTRY_INFOF("added large attachment \"%s\" (%zu MiB)",
+            sentry__attachment_get_filename(attachment), size / (1024 * 1024));
+    }
     attachment->type = attachment_type;
     attachment->content_type = sentry__string_clone(content_type);
 

src/sentry_attachment.h

@@ -5,7 +5,8 @@
 
 #include "sentry_path.h"
 
-#define SENTRY_LARGE_ATTACHMENT_SIZE (100 * 1024 * 1024) // 100 MB
+#define SENTRY_LARGE_ATTACHMENT_SIZE (100 * 1024 * 1024) // 100 MiB
+#define SENTRY_MAX_ATTACHMENT_SIZE (1024 * 1024 * 1024) // 1 GiB
 
 /**
  * The attachment_type.