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>

src/editor/ProjectSession.ts

@@ -47,6 +47,11 @@ export class ProjectSession {
     }
   }
 
+  /** Opens a project by its id – from the user management, where it may be somebody else's (#179). */
+  openProject(id: string): void {
+    void this.run(this.open(id));
+  }
+
   private async open(id: string): Promise<void> {
     this.beforeSwitch();
     const loaded = await this.store.load(id, this.prepare);
@@ -75,14 +80,18 @@ export class ProjectSession {
     if (id === this.state.project.id) await this.openFirstOrCreate();
   }
 
-  /** The one menu of the top bar (#183): everything that is about the project rather than a scene. */
-  openMainMenu(anchor: Widget): void {
+  /**
+   * The one menu of the top bar (#183): everything that is about the project rather than a scene.
+   * `more` comes last – what the editor adds that is not about the project (#179).
+   */
+  openMainMenu(anchor: Widget, more: MenuEntry[] = []): void {
     const items: MenuEntry[] = [
       { label: 'New project', onSelect: () => void this.run(this.createNext()) },
       { label: 'Open project…', onSelect: () => this.openProjectPicker() },
       { separator: true },
       { label: 'Project settings…', onSelect: () => this.openProjectSettings() },
       { label: 'Clear saved data', onSelect: () => this.clearSavedData() },
+      ...more,
     ];
     new Menu(items).openBelow(anchor);
   }