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/layouts/bots/(partials)/rail-settings-list.tsx

@@ -0,0 +1,32 @@
+import Divider from "@moduletrace/twui/layout/Divider";
+import { SettingsPages } from "@/src/dict/settings-pages-dict";
+import RailBackLink from "./rail-back-link";
+import RailSettingsLink from "./rail-settings-link";
+
+type Props = {
+    pathname?: string;
+};
+
+/**
+ * Settings mode of the rail: back to the bots, then the settings sub pages.
+ */
+export default function RailSettingsList({ pathname }: Props) {
+    const current = pathname?.replace(/\/$/, "");
+
+    return (
+        <>
+            <RailBackLink />
+            <Divider className="shrink-0 mx-1 lg:mx-3 my-2 w-auto border-hairline dark:border-hairline" />
+            {SettingsPages.map((page) => (
+                <RailSettingsLink
+                    key={page.url}
+                    {...page}
+                    selected={
+                        current == page.url ||
+                        Boolean(current?.startsWith(`${page.url}/`))
+                    }
+                />
+            ))}
+        </>
+    );
+}