remove: podman system migrate (wrong tool for the wrong problem)

It was added to "pick up subuid/subgid mappings" but that's not what it
does — it migrates container storage after a Podman version upgrade.
Subuid/subgid changes are picked up by restarting the Podman socket,
which the script already does. The only effect of running it was stopping
all containers on every platform start.

https://claude.ai/code/session_01FKCW3FDjNFj6jve4niMFXH

infra/boot.sh

@@ -54,7 +54,6 @@ fi
 [ -S "$PODMAN_SOCK" ] || { echo "ERROR: Podman socket did not appear"; exit 1; }
 
 # ── Bring up the stack ─────────────────────────────────────────────────────────
-podman system migrate
 podman compose --env-file "$REPO_ROOT/.env" -f "$SCRIPT_DIR/docker-compose.yml" up -d
 
 # ── Restart deployed app containers ───────────────────────────────────────────

infra/start.sh

@@ -127,8 +127,6 @@ fi
 if ! grep -q "^${_HIY_USER}:" /etc/subgid 2>/dev/null; then
     echo "${_HIY_USER}:100000:65536" | sudo tee -a /etc/subgid > /dev/null
 fi
-# NOTE: podman system migrate is intentionally deferred until just before
-# compose up so that running containers stay alive during the image build.
 
 # ── Allow rootless processes to bind ports 80/443 ─────────────────────────────
 # Rootless Podman cannot bind privileged ports (<1024) by default.
@@ -181,9 +179,6 @@ done
 make -C "$SCRIPT_DIR" build
 
 # ── Swap to new images (brief downtime starts here) ────────────────────────────
-# Migrate Podman storage to pick up current subuid/subgid mappings.
-# Doing this here (not earlier) keeps running containers alive during the build.
-podman system migrate
 podman compose --env-file "$REPO_ROOT/.env" -f "$SCRIPT_DIR/docker-compose.yml" down
 podman compose --env-file "$REPO_ROOT/.env" -f "$SCRIPT_DIR/docker-compose.yml" up -d