feat(v0.2): фазовые systemd-таргеты Stage 0/1/2 + splash/warmup + зонтик

P6.3: shturman.target → зонтик (Wants stage0/1/2). Новые: stage0/1/2.target,
shturman-splash.service (Before=shell, минимум зависимостей → «мгновенно»),
shturman-stage2-warmup.service (After=shell, маркер /run/shturman/stage2.ready),
tmpfiles-shturman.conf (/run/shturman). Члены critical set → stage1.target
(WantedBy+PartOf); у shell убран RuntimeDirectory (каталог теперь от tmpfiles).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Alexander <akotenev2003@gmail.com>

systemd/shturman-machineid.service

@@ -13,4 +13,4 @@ RemainAfterExit=yes
 ExecStart=/bin/sh -c '[ -e /etc/machine-id ] || : > /etc/machine-id; mount --bind /data/state/machine-id /etc/machine-id'
 
 [Install]
-WantedBy=shturman.target
+WantedBy=shturman-stage1.target