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.

README.md

@@ -89,8 +89,9 @@ no database, no data leaving your machine except the requests you send to Ollama
   why, **three progressive hints** per step (nudge → hint → the full answer), and a **checkpoint**
   built from the normal activity components and graded through `/api/grade`
 - The last screen assembles the solution from the step answers, with a copy button
-- Results live in `freezmo.homework.v1` with a small history you can reopen or delete; **Make it
-  again** re-runs from the stored assignment text — original files are never saved
+- Results live in `freezmo.homework.v1` — the homework screen's history and the library's
+  **Homework** tab — where you can reopen or delete them; **Make it again** re-runs from the
+  stored assignment text, and original files are never saved
 - The answer and the guide are always written in the **language of the assignment**, never
   translated into the interface language
 
@@ -116,6 +117,9 @@ no database, no data leaving your machine except the requests you send to Ollama
 
 **Library & folders**
 
+- **Two pools, never mixed**: a **Study Decks** tab (the folder + card library) and a **Homework**
+  tab with saved solutions and step-by-step guides — each with its own empty state and call to
+  action, and the active tab lives in the URL (`/?tab=homework`)
 - Decks saved locally with title, subject, folder, activity count, date, play count and best score
 - **Folders**: create named groups ("History", "Biology", …) from the sidebar or the create screen.
   New decks freeze straight into the selected folder; anything unfiled lives in **Unorganized**.