Add support for S3-backed image storage

conf/default.env

@@ -20,3 +20,18 @@ REPORT_EMAIL=
 SENT_CLEAN_AGE=
 # Delete all reminders after this many months
 TOTAL_CLEAN_AGE=
+
+# Optional dashboard image uploads. Leave these blank to use image URLs only.
+# All five S3 settings are required. The bucket/CDN must serve objects publicly.
+S3_BUCKET=
+S3_REGION=
+S3_ACCESS_KEY_ID=
+S3_SECRET_ACCESS_KEY=
+S3_PUBLIC_URL=
+# Optional S3-compatible endpoint (uses path-style addressing).
+S3_ENDPOINT=
+# NSFW moderation is enabled by default. Set false (or 0/off) to disable it.
+NSFW_CHECK_ENABLED=true
+# Seconds to retain an upload after cleanup first detects that it is orphaned.
+# Must be positive. Defaults to seven days when absent or blank.
+IMAGE_UPLOAD_ORPHAN_RETENTION_SECONDS=604800