Fix the mode-choice redundancy: standardized names, deep links, compact switch

Terminology (lib/i18n-dict.ts)
- One name per mode everywhere: "Study Deck" / "Studijní balíček" and
  "Homework Solver" / "Řešitel úkolů". The library empty-state cards and the
  /create switcher now read the same, so the choice no longer changes name
  between screens.

Deep links
- Library quick actions carry the mode: /create?mode=deck and
  /homework?mode=homework.
- Both pages canonicalize: /create?mode=homework redirects to the homework
  flow and /homework?mode=deck redirects to /create, so a mode link always
  opens that mode directly.

/create
- The two bulky square cards (106px tall, wrapping/clipping "Study Deck &
  Qu…" on phones) are replaced by a compact segmented control (52px) placed
  directly above "1. Add your notes": ice pill, snowflake/sparkles icons,
  44px segments and one-line labels at 360px. The pill slides to the chosen
  segment and the route follows ~190ms later, so toggling reads as one smooth
  transition (immediate under prefers-reduced-motion).

Service worker: freezmo-v9.

Verified: mode-switch suite 26/26 (deep links, cross-mode redirects, 52px
control, 44px segments, no clipping/wrapping at 360px, "1. Add your notes" at
y=394 of 740 with the upload controls above the fold, pill slide, axe contrast,
en+cs, phone+desktop), mobile 49/49, i18n 27/27, desktop regression 73/73.
Lint + build clean.

app/homework/page.tsx

@@ -1,3 +1,5 @@
+import { redirect } from "next/navigation";
+
 import { ApiKeyGate } from "@/components/ApiKeyGate";
 import { AppHeader } from "@/components/AppHeader";
 import { HomeworkScreen } from "@/components/homework/HomeworkScreen";
@@ -8,7 +10,16 @@ export const metadata = {
   title: "Make my homework",
 };
 
-export default function HomeworkPage() {
+export default async function HomeworkPage({
+  searchParams,
+}: {
+  searchParams: Promise<{ [key: string]: string | string[] | undefined }>;
+}) {
+  const { mode } = await searchParams;
+  // The mode switch and the library quick actions deep-link into a mode; a
+  // link that points at the Study Deck side is handed back to /create.
+  if (mode === "deck") redirect("/create?mode=deck");
+
   return (
     <ApiKeyGate>
       <div className="flex min-h-dvh">