Make Cobble a local install: setup flow, bots-first admin, settings

Local, password-only auth:
- No public pages; everything outside /admin and /auth redirects in
- First run (no users) sends every page to /auth/signup, which creates
  the super admin (user #1) once and then locks
- Login is email/username + password; removed the emailed-code flow,
  /auth/sso and email password reset
- Google login kept for existing accounts only, never creates them
- seed-super-admin now requires SEED_SUPER_ADMIN_PASSWORD

Bots-first admin:
- /admin and closed sections (people, logs, backups) redirect to
  /admin/bots; only bots and settings are live (AdminSections)
- Removed the old admin layout; every /admin page uses the bots rail
- Coordinator bot created at signup/seed and by /admin/bots
  (ensureCoordinatorBot), which redirects to its chat
- bots.system_prompt (markdown) with a default coordinator prompt
- seed-bots reuses the existing coordinator

Settings:
- Sub pages general (default), profile, change-password, listed in the
  rail with a back link; unknown settings paths redirect to general
- Redesigned settings UI: pane header, grouped rows, sticky save bar
- General: System/Light/Dark theme, saved per device

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/pages/__root.tsx

@@ -10,7 +10,6 @@ import type {
 import type { AppContextObject, AppStateObject } from "@/src/types";
 import { SiteData } from "@/src/data/site-data";
 import Layout from "../layouts/main";
-import AdminLayout from "../layouts/admin";
 import AuthLayout from "../layouts/auth";
 import BotsLayout from "../layouts/bots";
 import ThemeInitScript from "../components/general/theme-init-script";
@@ -47,18 +46,10 @@ export default function App({
         query,
     };
 
-    if (url?.pathname.startsWith("/admin/bots")) {
-        return (
-            <AppContext.Provider value={appContextObject}>
-                <BotsLayout>{children}</BotsLayout>
-            </AppContext.Provider>
-        );
-    }
-
     if (url?.pathname.startsWith("/admin")) {
         return (
             <AppContext.Provider value={appContextObject}>
-                <AdminLayout>{children}</AdminLayout>
+                <BotsLayout>{children}</BotsLayout>
             </AppContext.Provider>
         );
     }