Add Phase 6: multi-server admin panel (server registry + settings)

Gate a new /api/admin/* route set (register/list/update/delete servers)
behind a single shared MCMAPPER_ADMIN_TOKEN header, and add a /admin
frontend page (Alpine) to unlock, register new servers, and edit
authMode/anonymousChatAllowed/waypointFormat per server — these columns
already existed but were only editable via direct DB edit until now.

Written test-first per the project's TDD workflow: admin.ts's domain
logic, the index.ts route wiring, and a new e2e/tests/admin.spec.ts
covering the token gate and register/edit/delete round trip through the
real browser UI.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015tKdPZt78zbPUZMXWzKEKt

e2e/global-setup.ts

@@ -12,6 +12,7 @@ import { execSync, spawn, type ChildProcess } from "node:child_process";
 import { writeFileSync } from "node:fs";
 import postgres from "postgres";
 import {
+  ADMIN_TOKEN,
   API_DIR,
   API_PORT,
   DATABASE_URL,
@@ -145,6 +146,7 @@ export default async function globalSetup() {
     MINIO_USE_SSL: "false",
     MINIO_ACCESS_KEY,
     MINIO_SECRET_KEY,
+    MCMAPPER_ADMIN_TOKEN: ADMIN_TOKEN,
   });
   await waitFor(() => httpOk(`http://localhost:${API_PORT}/health`), "api");
 
@@ -171,6 +173,7 @@ export default async function globalSetup() {
       serverToken,
       sessionToken,
       accountId: account!.id,
+      adminToken: ADMIN_TOKEN,
     }),
   );