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/admin/settings/general/(partials)/theme-option.tsx

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+import Button from "@moduletrace/twui/layout/Button";
+import Span from "@moduletrace/twui/layout/Span";
+import Stack from "@moduletrace/twui/layout/Stack";
+import { Check } from "lucide-react";
+import { twMerge } from "tailwind-merge";
+import type { ThemePreferences } from "@/src/dict/theme-preferences-dict";
+
+type Props = (typeof ThemePreferences)[number] & {
+    selected: boolean;
+    onSelect: () => void;
+};
+
+/**
+ * One radio tile. Selected is a strong border plus a check, so it never
+ * depends on color alone.
+ */
+export default function ThemeOption({
+    title,
+    description,
+    Icon,
+    selected,
+    onSelect,
+}: Props) {
+    return (
+        <Button
+            title={title}
+            type="button"
+            role="radio"
+            aria-checked={selected}
+            variant="ghost"
+            color="gray"
+            onClick={onSelect}
+            className={twMerge(
+                "relative w-full min-w-0 h-auto p-4! pr-10! justify-start! rounded-default text-left",
+                "bg-surface dark:bg-surface hover:bg-sunken hover:dark:bg-sunken text-ink dark:text-ink",
+                "border border-solid border-hairline transition-colors duration-[var(--m-fast)]",
+                "focus-visible:ring-2 focus-visible:ring-ink focus-visible:ring-offset-2 focus-visible:ring-offset-paper",
+                selected && "border-ink dark:border-ink bg-ink/5 dark:bg-ink/5",
+            )}
+        >
+            <Stack className="w-full min-w-0 gap-3! items-start">
+                <Icon size={20} aria-hidden />
+                <Stack className="w-full min-w-0 gap-0! items-start">
+                    <Span className="text-sm font-bold leading-5 text-ink">
+                        {title}
+                    </Span>
+                    <Span className="text-[13px] leading-[18px] text-ink-secondary">
+                        {description}
+                    </Span>
+                </Stack>
+            </Stack>
+            {selected ? (
+                <Span className="absolute top-3 right-3 size-5 rounded-full bg-ink text-on-ink flex items-center justify-center">
+                    <Check size={12} strokeWidth={3} aria-hidden />
+                </Span>
+            ) : null}
+        </Button>
+    );
+}

src/pages/admin/settings/general/(partials)/theme-picker.tsx

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+import Row from "@moduletrace/twui/layout/Row";
+import { ThemePreferences } from "@/src/dict/theme-preferences-dict";
+import useThemePreference from "@/src/hooks/use-theme-preference";
+import ThemeOption from "./theme-option";
+
+/**
+ * Applies on click; there is nothing to save.
+ */
+export default function ThemePicker() {
+    const { preference, setPreference } = useThemePreference();
+
+    return (
+        <Row
+            role="radiogroup"
+            aria-label="Theme"
+            className="w-full grid grid-cols-1 sm:grid-cols-3 gap-3!"
+        >
+            {ThemePreferences.map((option) => (
+                <ThemeOption
+                    key={option.value}
+                    {...option}
+                    selected={preference == option.value}
+                    onSelect={() => setPreference(option.value)}
+                />
+            ))}
+        </Row>
+    );
+}

src/pages/admin/settings/general/(sections)/appearance-section.tsx

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+import SettingsGroup from "../../(partials)/settings-group";
+import ThemePicker from "../(partials)/theme-picker";
+
+export default function AppearanceSection() {
+    return (
+        <SettingsGroup
+            title="Theme"
+            description="Saved on this device only, so each computer can have its own."
+        >
+            <ThemePicker />
+        </SettingsGroup>
+    );
+}

src/pages/admin/settings/general/index.server.ts

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+import type { PagePropsType } from "@/src/types";
+import type { BunextPageServerFn } from "@moduletrace/bunext/types";
+import grabSettingsServerProps from "../(functions)/grab-settings-server-props";
+
+export const server: BunextPageServerFn<PagePropsType> = async (params) => {
+    return await grabSettingsServerProps(params);
+};

src/pages/admin/settings/general/index.tsx

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+import AppearanceSection from "./(sections)/appearance-section";
+import SettingsShell from "../(partials)/settings-shell";
+import settingsPageMeta from "../(functions)/settings-page-meta";
+
+export default function AdminSettingsGeneralPage() {
+    return (
+        <SettingsShell
+            title="General"
+            description="How the app looks and behaves."
+        >
+            <AppearanceSection />
+        </SettingsShell>
+    );
+}
+
+export const meta = settingsPageMeta({ label: "General" });