Separate Study Decks and Homework in the library; drop the /create mode switch

Library ("Your icebox")
- Two tabs, never mixed: Study Decks (the folder + card library) and Homework
  (saved solutions and step-by-step guides). The active tab lives in the URL
  (/?tab=homework), so the sections are linkable and survive a reload.
- Decks tab keeps Import, the folder bar, stats and its own empty state — now
  a single decks-only CTA.
- Homework tab lists saved results as cards (mode icon, date, step count,
  preview) with Open and delete-with-confirm; its empty state has its own CTA
  ("Homework Solver") that opens the solver directly. Opening a card
  deep-links to /homework?open=<id>, which the screen opens on arrival.
- .segmented now also styles link segments (same control as settings).

/create
- The redundant "Study Deck | Homework Solver" toggle is gone: /create is the
  deck uploader only, and the bottom bar's + goes straight to it. Homework has
  its own screen, reached from the library tab, the drawer and CTAs.

Copy
- New keys (en + cs): tabDecks, tabHomework, homeworkHeroTitle, plus homework
  empty-state/open/step-count strings. The homework hero is now "Solve your
  homework" / "Vyřeš svůj úkol" — no study-deck text in the homework flow.
- Removed the now-unused ModeSwitch component and homework.title key.

Service worker: freezmo-v10.

Verified: library-tabs suite 37/37 (tab switching, context empty states,
deep-link opening, deletion, no switch on /create, heroes, redirects, desktop
grid, 360px + 44px targets, axe contrast en+cs light+dark), mobile 49/49,
i18n 27/27, desktop regression 74/74. Lint + build clean.

components/UploadScreen.tsx

@@ -33,7 +33,6 @@ import { upsertDeck } from "@/lib/storage";
 import { openSettings } from "@/lib/ui-events";
 import { cn, uid } from "@/lib/utils";
 import { CameraIcon, FolderIcon, IceCubeIcon, PlusIcon, SnowflakeIcon, SunIcon } from "@/components/icons";
-import { ModeSwitch } from "@/components/ModeSwitch";
 import { Button, ProgressBar } from "@/components/ui";
 
 type Phase = "idle" | "preparing" | "loading" | "error";
@@ -321,9 +320,9 @@ export function UploadScreen() {
           </p>
         </section>
 
-        {/* Mode switcher: a compact segmented control. This page is the Study
-            Deck side; the other segment opens the homework flow. */}
-        <ModeSwitch current="deck" />
+        {/* Dedicated flow: this page is the Study Deck uploader. Homework has
+            its own screen (/homework), reached from the library tab, the
+            drawer or the bottom bar — no mode picker here. */}
 
 
         {error ? (