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/panels/assetIcons.ts

@@ -25,6 +25,7 @@ import text from './icons/text.svg?raw';
 import texture from './icons/texture.svg?raw';
 import tile from './icons/tile.svg?raw';
 import tilemap from './icons/tilemap.svg?raw';
+import users from './icons/users.svg?raw';
 import variables from './icons/variables.svg?raw';
 import vectorart from './icons/vectorart.svg?raw';
 
@@ -60,3 +61,6 @@ export const GAME_ICON_SVG = game;
 
 /** The Plugins tab's: a puzzle piece, as a plugin is a piece added to the editor (#119). */
 export const PLUGINS_ICON_SVG = plugins;
+
+/** The User management tab's (#179), which holds the plugins as well; an account sees it only as an administrator. */
+export const USERS_ICON_SVG = users;

src/editor/panels/icons/users.svg

@@ -0,0 +1,19 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="-8 -8 16 16" width="16" height="16">
+  <!-- The User management tab (#179): two people, the one behind cut off by the one in front.
+       Shoulders are cubic curves, not arcs: Pixi's parser draws an A after an L as a spike. -->
+  <circle cx="-1.5" cy="-2.5" r="2.5" fill="none" stroke="currentColor" stroke-width="1.5" />
+  <path
+    d="M-6.5 6.5 C-6.5 2.5 -4.5 1 -1.5 1 C1.5 1 3.5 2.5 3.5 6.5"
+    fill="none"
+    stroke="currentColor"
+    stroke-width="1.5"
+    stroke-linecap="round"
+  />
+  <path
+    d="M3.2 -6.2 C5 -6 5.9 -4.8 5.9 -3.5 C5.9 -2.2 5 -1 3.4 -0.8 M5.2 1.3 C6.8 2 7.4 3.8 7.4 6"
+    fill="none"
+    stroke="currentColor"
+    stroke-width="1.5"
+    stroke-linecap="round"
+  />
+</svg>