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/data/coordinator-system-prompt.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, test } from "bun:test";
+import { CoordinatorSystemPrompt } from "./coordinator-system-prompt";
+import { SiteData } from "./site-data";
+
+describe("CoordinatorSystemPrompt", () => {
+    test("is markdown that opens with the coordinator heading", () => {
+        expect(CoordinatorSystemPrompt.startsWith("# You are the Coordinator")).toBe(
+            true,
+        );
+        expect(CoordinatorSystemPrompt).toContain("## Rules");
+    });
+
+    test("names the product from SiteData, with no em dashes", () => {
+        expect(CoordinatorSystemPrompt).toContain(SiteData["SiteName"]);
+        expect(CoordinatorSystemPrompt).not.toContain(String.fromCharCode(0x2014));
+    });
+});