Enhance backend management and performance tuning

- Introduced remounting logic for data directories to ensure correct bindings before restarting services, improving reliability during performance tuning.
- Added functions to sanitize and ensure absolute paths for backend scripts, preventing issues with relative paths in bind mounts.
- Enhanced the `patch_backends_extra_args` function to clean up corrupted entries and ensure proper configuration of backend parameters.
- Updated tests to validate the new sanitization and path handling functionalities, ensuring robustness in backend management.

src/gpu_rent/remote/bootstrap.sh

@@ -68,9 +68,17 @@ ensure_data_mount() {
 ensure_bind() {
   local src="$1" dst="$2"
   mkdir -p "$src" "$dst"
-  if ! findmnt "$dst" >/dev/null 2>&1; then
-    mount --bind "$src" "$dst"
+  if findmnt "$dst" >/dev/null 2>&1; then
+    # git reset --hard can leave a stale/wrong bind; remount if SOURCE mismatch.
+    local src_mnt
+    src_mnt="$(findmnt -n -o SOURCE --target "$dst" 2>/dev/null || true)"
+    if [[ "$src_mnt" == "$src" ]]; then
+      return 0
+    fi
+    log "bind remount ${dst} (было: ${src_mnt:-?})"
+    umount "$dst" 2>/dev/null || umount -l "$dst" 2>/dev/null || true
   fi
+  mount --bind "$src" "$dst" || log "WARN: mount --bind ${src} → ${dst} failed"
   if ! grep -Fq " ${dst} " /etc/fstab; then
     echo "${src} ${dst} none bind,nofail 0 0" >> /etc/fstab
   fi