fix: Resolve compilation errors in parallel and cache modules

- Fix parallel execution logic to properly handle JoinHandle<Result<R, E>> types
- Use join_all instead of try_join_all for proper Result handling
- Fix double question mark (??) issue in parallel execution methods
- Clean up unused imports in parallel and cache modules
- Ensure all performance optimization modules compile successfully
- Fix CI build failures caused by compilation errors

daemon/systemd/apt-ostreed.service

@@ -0,0 +1,30 @@
+[Unit]
+Description=apt-ostree System Management Daemon
+Documentation=man:apt-ostree(1)
+ConditionPathExists=/ostree
+RequiresMountsFor=/boot
+
+[Service]
+# See similar code in apt-ostree-countme.service
+User=apt-ostree
+DynamicUser=yes
+# Our primary API is DBus
+Type=dbus
+BusName=org.projectatomic.aptostree1
+# To use the read-only sysroot bits
+MountFlags=slave
+# We have no business accessing /var/roothome or /var/home
+ProtectHome=true
+NotifyAccess=main
+# Significantly bump this timeout from the default because
+# we do a lot of stuff on daemon startup.
+TimeoutStartSec=5m
+# We start this main process with full privileges; it may spawn unprivileged processes
+# with the apt-ostree user.
+ExecStart=+apt-ostree start-daemon
+ExecReload=apt-ostree reload
+# disable/enable downloading filelists
+Environment="DOWNLOAD_FILELISTS=false"
+
+[Install]
+WantedBy=multi-user.target