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/utils/is-admin-section-path.test.ts

@@ -0,0 +1,19 @@
+import { describe, expect, test } from "bun:test";
+import isAdminSectionPath from "./is-admin-section-path";
+
+describe("isAdminSectionPath", () => {
+    test("allows live sections and their sub pages", () => {
+        expect(isAdminSectionPath({ pathname: "/admin/bots" })).toBe(true);
+        expect(isAdminSectionPath({ pathname: "/admin/bots/3" })).toBe(true);
+        expect(isAdminSectionPath({ pathname: "/admin/settings/change-password" })).toBe(
+            true,
+        );
+    });
+
+    test("rejects the admin root, closed sections and lookalikes", () => {
+        expect(isAdminSectionPath({ pathname: "/admin" })).toBe(false);
+        expect(isAdminSectionPath({ pathname: "/admin/people" })).toBe(false);
+        expect(isAdminSectionPath({ pathname: "/admin/logs" })).toBe(false);
+        expect(isAdminSectionPath({ pathname: "/admin/botsx" })).toBe(false);
+    });
+});