fix: use apt --reinstall to handle restored dpkg state

Restoring /var/lib/dpkg/ makes apt think packages are installed when
the actual binaries are not synced. Use --reinstall to force.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

entrypoint.py

@@ -157,7 +157,7 @@ def restore():
         to_install = sorted(saved - base)
         if to_install:
             log(f"── RESTORE: apt install {len(to_install)} packages")
-            rc, _ = sh(f"apt-get update -qq && apt-get install -y --no-install-recommends {' '.join(to_install)}")
+            rc, _ = sh(f"apt-get update -qq && apt-get install -y --reinstall --no-install-recommends {' '.join(to_install)}")
             if rc == 0:
                 log(f"  packages restored")
             else: