fix: point dump_db.sh at its /opt/backup-agent deploy path, remove healthcheck

dump_db.sh no longer lives under $TARGET, so its own default dump
directory (relative to wherever the script is) would land outside the
backed-up tree. Pin DUMP_SCRIPT to /opt/backup-agent/dump_db.sh and
export DUMP_DIR explicitly so dumps still land in $TARGET/mariadb/dump
regardless of where the script itself is deployed.

Also drop the healthcheck integration (HEALTHCHECK_URL, send_healthcheck,
curl requirement) from borg-backup.sh per request - no monitoring hook
wanted for now.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

borg-backup.sh

@@ -25,6 +25,12 @@ NAME="borg-2025"
 REPO="/home/srv/files/backups/$NAME"
 TARGET="/home/srv/files/content"
 
+# dump_db.sh lives with the rest of this toolkit, not inside $TARGET - its
+# own default dump dir is relative to wherever IT lives, so DUMP_DIR must be
+# passed explicitly (below) to keep dumps inside $TARGET where borg can see them.
+DUMP_SCRIPT="/opt/backup-agent/dump_db.sh"
+export DUMP_DIR="${TARGET}/mariadb/dump"
+
 REPO_MOUNT=""
 
 LOGDIR="/var/log/borg"
@@ -217,8 +223,6 @@ preflight
 
 # --- 1. Logical dumps (container stays up the whole time) ---------------
 step "Step 1: MariaDB dumps"
-DUMP_SCRIPT="${TARGET}/mariadb/dump_db.sh"
-DUMP_DIR="${TARGET}/mariadb/dump"
 
 if [[ ! -x "$DUMP_SCRIPT" ]]; then
     log "ERROR: dump script missing or not executable: $DUMP_SCRIPT"