feat(settings): a Pet page for the mascot

Settings -> Pet (/settings/pet, PetSettings.tsx): show/hide, speech
bubbles, size with a live preview, and the pet grid - Sagi, featured
codex-pets.net pets (downloaded on first pick), your own (deletable) -
with image upload and .codex-pet.zip import. The Sagi block leaves
General; the mascot menu's Pet settings opens the page. PetMenu and the
page share components/Sagi/usePets.ts.

client/src/pages/SettingsHub.tsx

@@ -24,6 +24,7 @@ import {
   KeyRound,
   Orbit,
   Palette,
+  PawPrint,
   Puzzle,
   Router,
   Search,
@@ -37,6 +38,7 @@ import { AiToolConfig } from "./AiToolConfig";
 import { AiRouterConfig } from "./AiRouterConfig";
 import { GitCredentialsConfig } from "./GitCredentialsConfig";
 import { AppearanceSettings } from "../components/settings/AppearanceSettings";
+import { PetSettings } from "../components/settings/PetSettings";
 import { AiToolsSettings } from "../components/settings/AiToolsSettings";
 import { PricingSettings } from "../components/settings/PricingSettings";
 import { WorktreeVisibilitySettings } from "../components/settings/WorktreeVisibilitySettings";
@@ -106,6 +108,13 @@ export function SettingsHub() {
       ...s("appearance"),
       render: () => <AppearanceSettings />,
     },
+    {
+      id: "pet",
+      group: "general",
+      Icon: PawPrint,
+      ...s("pet"),
+      render: () => <PetSettings />,
+    },
     {
       id: "notifications",
       group: "general",