fix(cost): bill a session outside every workspace to its Linux account's user

A script's claude -p in a temp folder (the SG Flow eval runner strips the
pane's env) had no workspace, so its spend reached nobody's Today, the Users
page or a spend quota — ~$57 of a $74 day was missing from the status bar.

sessions.account records the Linux account a session ran as (the hook's
peer uid, else its folder for poller-made and old rows); a session no
workspace owns is owned by that account's user — a member's to them, the
host's to the admin ticked 'Owns this server's host account' (or the only
admin). Workspace ownership still wins.

server/db.js

@@ -1445,6 +1445,16 @@ try {
   db.prepare("ALTER TABLE sessions ADD COLUMN pinned_at TEXT").run();
 }
 
+// Migrate: add `account` to sessions — the Linux account a session ran as
+// (server/lib/session-account.js): "" = the host's, else the S3 member's name;
+// NULL = not known yet. A session no workspace owns is billed to the user of
+// that account (server/lib/scope.js), so a script's `claude -p` still counts.
+try {
+  db.prepare("SELECT account FROM sessions LIMIT 1").get();
+} catch {
+  db.prepare("ALTER TABLE sessions ADD COLUMN account TEXT").run();
+}
+
 // How far each Codex rollout journal has been read (server/lib/codex-usage.js).
 // In the DB, not a side file, so a session the user deleted stays deleted
 // until Codex writes to its journal again, while a wiped DB re-imports all.
@@ -1952,6 +1962,9 @@ for (const col of ["display_name", "email", "avatar_at", "avatar_link"]) {
 for (const [col, type] of [
   ["last_login_at", "TEXT"],
   ["must_change_password", "INTEGER NOT NULL DEFAULT 0"],
+  // The admin who owns the HOST's Linux account: its sessions outside every
+  // workspace are billed to them (server/lib/session-account.js). At most one.
+  ["host_account", "INTEGER NOT NULL DEFAULT 0"],
 ]) {
   try {
     db.prepare(`SELECT ${col} FROM users LIMIT 1`).get();