Archive the whole data volume in Backups, not just the database

Settings > Backups gains a whole-data archive beside the database
snapshots, and both lists now fully work from the page.

- Data archives: `write-data-backup-archive.ts` tars all of DATA_DIR into
  BACKUP_ARCHIVE_DIR as cobble-data-<epoch-ms>.tar.gz, every entry under one
  root folder named after the archive, writing a .part name and renaming on
  success so a cut-off run is never listed. The newest
  AppData.DataBackupsKept are kept; db/.backups is left as it is.
- Restore: `restore-data-backup.ts` extracts to a temp dir, requires one
  root folder holding a db folder, takes a safety archive first, then
  replaces DATA_DIR (the database snapshots included) and `restart-app.ts`
  restarts the process through the docker socket, since the open SQLite
  handle points at the replaced file.
- Upload and restore: a modal over each list (database file or data
  archive), replacing the old /admin/settings/backups/restore page.
- Delete for both kinds, icon-only row actions shared through
  RowIconButton, and restore on every row.
- One backup or restore of either kind at a time (with-backup-run-lock).
- BACKUP_ARCHIVE_DIR is a start-up path (ProcessOnlyEnvKeys); the installer
  mounts $COBBLE_HOME/backups-archives at /backups-archives and recreates a
  container that lacks it. The image installs tar and gzip.

src/utils/grab-backup-archive-dir.ts

@@ -0,0 +1,27 @@
+import fs from "fs";
+import os from "os";
+import path from "path";
+
+/**
+ * Absolute path of the directory the whole-data archives are written to.
+ * It is deliberately outside `DATA_DIR` (an archive must never contain
+ * other archives) and outside the database's own `db/.backups`
+ * directory, which keeps its bun-sqlite snapshots.
+ *
+ * `BACKUP_ARCHIVE_DIR` is the container's or install's setting (the
+ * installer mounts `/backups-archives` from `$COBBLE_HOME/backups-archives`);
+ * outside docker it falls back to `~/.cobble/backups`. It is a start-up
+ * path like `DATA_DIR`, so it stays in the process environment and is
+ * never an `envs` row.
+ */
+export default function grabBackupArchiveDir() {
+    const dir =
+        process.env.BACKUP_ARCHIVE_DIR ||
+        path.join(os.homedir(), ".cobble", "backups");
+
+    if (!fs.existsSync(dir)) {
+        fs.mkdirSync(dir, { recursive: true });
+    }
+
+    return path.resolve(dir);
+}