Add roles and a user management tab for admins (#180, #179)

Until now every account could do the same, and managing accounts
meant running make-user.php on the server. Accounts now carry a role,
and admins get a tab in the editor to create, rename, re-role, reset
and delete accounts. Both issues share the same server files, so they
land in one commit.

#180 Roles:
- Every account is admin or user. A missing or unknown role counts as
  user, on the server and in the client.
- auth/session and auth/login return {user, role}.
- Auth::requireAdmin() answers everyone else with 403.
- make-user.php takes the role as a third argument. Without it an
  existing account keeps its role, so a password reset from the CLI
  never demotes an admin.
- Admins see and save other users' projects like their own. Saving
  keeps the original owner.

#179 User management:
- The account menu gets "User management" (admins only) and "Plugins"
  (everyone). Both open the same closable tab, accounts on top and
  plugins below. The fixed Plugins tab is gone.
- Per account: Rename, Role, Password (no old password needed) and
  Delete with a confirmation. "New user..." creates one.
- Each account lists its projects with an Open button.
- Delete is refused while the account still owns projects.
- Renaming moves the projects along and ends every session of the
  account. transfer takes the same lock as save.
- On their own row an admin can only set the password. The last admin
  cannot be demoted or deleted. The server enforces both.
- The account rules live in AccountRules.php and accountRules.ts as
  pure functions, so they are testable without a server.

Findings:
- At 1280 px the Delete button reached past the column edge and was
  not clickable. The name column is flexible now, and module 49 checks
  the layout.
- The server lets an admin delete other users' projects, but the
  editor has no button for it yet. Left open in the issue.

Tests:
- ./check.sh: 148 files, 2214 tests, exit 0 (was 147 / 2204).
- New tests/php/accounts.test.php, 51 checks, plain PHP. CI runs it
  as its own step in the gate job, the host has no PHP.
- New e2e module 49 with 18 checks. CI creates the e2e-admin account
  in serve.sh. Modules 14, 38, 46 and the scaffold follow the new tab.
- e2e 1-16,37,38,45,46,49: all passed, 581 checks.
- Counter-checks: owner on save, admin view, default role and self
  delete in PHP fail 7, 5, 5 and 1 checks. Unchecked requireAdmin,
  a wider column and the caller as owner each fail exactly their
  e2e check.
- Check sum 1314 -> 1333 (+1 in 38, +18 in 49), computed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/make-user.php

@@ -2,10 +2,12 @@
 declare(strict_types=1);
 
 /**
- * Creates an account or sets the password of one that exists. The API has no route for it:
- * signing up is a follow-up issue, so until then accounts are made here, on the server.
+ * Creates an account or sets the password of one that exists – the way to the first administrator,
+ * who can then manage the others in the editor (#179).
  *
- * Usage: php tools/make-user.php <username> <password>
+ * Without a role a new account is a `user` and an existing one keeps its role (#180).
+ *
+ * Usage: php tools/make-user.php <username> <password> [admin|user]
  *        php tools/make-user.php --list
  */
 
@@ -16,21 +18,26 @@ $store = new UserStore($file);
 
 $args = array_slice($argv, 1);
 if (($args[0] ?? '') === '--list') {
-    foreach ($store->names() as $name) {
-        echo $name, "\n";
+    foreach ($store->accounts() as $account) {
+        echo $account['username'], ' ', $account['role'], "\n";
     }
     exit(0);
 }
-if (count($args) !== 2 || $args[0] === '' || $args[1] === '') {
-    fwrite(STDERR, "Usage: php tools/make-user.php <username> <password>\n");
+if (count($args) < 2 || count($args) > 3 || $args[0] === '' || $args[1] === '') {
+    fwrite(STDERR, "Usage: php tools/make-user.php <username> <password> [admin|user]\n");
     exit(2);
 }
 
 [$username, $password] = $args;
+$role = $args[2] ?? null;
 if (!UserStore::isValidName($username)) {
     fwrite(STDERR, "Invalid user name: {$username}\n");
     exit(2);
 }
+if ($role !== null && !UserStore::isValidRole($role)) {
+    fwrite(STDERR, "Unknown role: {$role} (admin or user)\n");
+    exit(2);
+}
 $existed = $store->exists($username);
-$store->put($username, $password);
-echo ($existed ? 'password set for ' : 'created '), $username, "\n";
+$store->put($username, $password, $role);
+echo ($existed ? 'password set for ' : 'created '), $username, ' (', $store->role($username), ")\n";